WO1993021703A1

WO1993021703A1 - Signal distribution system

Info

Publication number: WO1993021703A1
Application number: PCT/AU1993/000168
Authority: WO
Inventors: David Ian Spalding; John Ashley Seymour
Original assignee: Coachline Video Express Pty Ltd
Priority date: 1992-04-15
Filing date: 1993-04-14
Publication date: 1993-10-28
Also published as: CN1088035A

Abstract

A signal distribution system (200) is disclosed in which a programme source (204) is communicated via a transmission system (210) to a plurality of personal receiver units (220) which are configured to reproduce a signal derived from the source (204). The receiver units (220) each include a time unit store (23) containing a time unit value which, where greater than a predetermined amount, enables the receiver unit (22) to reproduce the signal. The time unit value is periodically decremented whilst the receiver unit (22) is in use until such time as the time unit value falls below the predetermined amount and the receiver unit is disabled. A vending system (202) is provided by which a user can purchase time units which are retained in the store (23) enabling further use of the receiver unit (220). A secure transmission arrangement (24) (fig. 10) and a transceiver apparatus (304) (fig. 13) are also disclosed.

Description

SIGNAL DISTRIBUTION SYSTEM Field^' of the Invention

The present invention relates to signal distribution systems and, in particular, discloses an arrangement which permits time-based vending of signals that are useful for a variety of purposes. Background Art

Audio distribution systems are well known in the art and have been widely used for the provision of in-flight entertainment in commercial airlines, and more recently similar principles have been applied to long distance coach and rail transport. Generally, such an arrangement requires the user to hire a pair of headphones which can then be plugged into a distribution outlet arranged adjacent the seat within the cabin of the aircraft, coach or train. The user then has the ability to select a particular channel being broadcast within the cabin and to adjust the volume of the sound output in the headphones.

Such an arrangement, although satisfactory in terms of performance, is not without its drawbacks. Firstly, because the headphones are hired, it is required to provide human resources for the distribution of the headphones before or during the journey and for their collection at the end of the journey. Also, for health reasons, it is required that the headphones be cleaned, or as is recently the practice, the headphone pads are replaced.

A further disadvantage of this system lies in distribution of sound via user accessible sockets into which the headphone sets are plugged. The sockets represent an attraction to vandals and this is a significant reason as to why such distribution systems are not in common use in public transport systems as opposed to the more exclusive airline, coach and long distance rail networks. Furthermore, the cost of a wiring network and in some cases its weight, is also significant. In order for audio distribution systems to infiltrate public transport networks and the like, it is desirable that a means be provided by which costs of installation and operation can be recovered without extending the necessity of human intervention such as with point of use hiring. A substantially vandal-proof arrangement is also desirable. Furthermore, there are many electronic systems which utilize services which essentially go unremitted by the user. Examples of this include normal radio and television reception, and GPS navigation systems. In this manner, once the receiver has been purchased, the user is free to receive signals with no payment to the supplier. Cable television systems have attempted to overcome this problem but the capital cost of such systems can be prohibitive to their implementation. Summary of the Invention It is an object of the present invention to substantially overcome, or ameliorate, some or all of the abovementioned difficulties through provision of a signal distribution system which permits use thereof according to a time related cost.

In accordance with the present invention there is disclosed a signal distribution system comprising: a transmission arrangement configured to transmit a signal derived from a source; and at least one receiver unit adapted to receive said signal, said receiver unit comprising: a time unit store for storing a time unit value derived from a time unit dispensing system; control means for reading the time unit value and if the value is greater than a predetermined amount, reception of said signal is enabled; and update means for varying the time unit value.

In accordance with a first aspect of the present invention there is disclosed a time vending signal distribution system comprising a source and at least one receptor unit adapted to receive one or more information signals and a time vending signal output from said source, said receptor unit comprising a control means adapted to retain a record of a time unit value modified by said time vending signal, wherein said control means is adapted to use said time unit value to enable operation of said receptor unit to receive said information signals for a predetermined period of time to provide a useful output of said receptor unit. Preferably, the time vending signal is integral with said information signal. Generally, the information signal can include a periodic time unit signal which is adapted to alter the time unit value to cause disabling of said receptor unit to receive said information signals after said predetermined period of time. Generally, the source can be a radio frequency (RF) transmitter, or a hard-wired distributed communication system. The receptor unit can include a RF receiver or a device directly connectable to the distributed systems. In accordance with a second aspect of the present invention there is disclosed a headphone means comprising: reproducing means for reproducing a transmitted audio programme signal as an acoustic signal; and controller means adapted for programming with a user selected number of time vending units, said units being compared with a periodic time vending signal enabled through use of said headphone means such that said controller means disables said reproducing means when a time period of use equivalent to said units has been expended. The audio program signal can be transmitted either as a radio frequency signal or using magnetic induction or alternatively can be provided through a distributed hard wired system.

In accordance with a third aspect of the present invention there is disclosed a time vending audio distribution system comprising: a headphone means in accordance with the second aspect; and transmission means arranged to transmit at least one said audio programme signal .

For example, the time vending signal can be received by said headphone means as a signal integral with, or in addition to, said audio programme signal. Alternatively, the time vending signal can be a clock signal internally generated within said controller means. In either case, the receipt of said time vending signal can be used to decrement said units until a nil unit value is reached, or, to increment a counter for comparison with the programmed number of said units. Preferably, the headphone means includes a pickup means adapted to receive energy transmitted by said transmission means and to convert same into electrical energy for the powering of said reproducing means and said controller means. Alternatively, or in addition to the pickup means, the headphone means can be powered by a battery source. Furthermore, the headphone means can be powered and supplied directly from a hard wired system.

Generally, the reproducing means includes a receiver means for receiving said audio programme signal and, in some embodiments, the receiver means and pickup means are formed by a single device. Also, the headphone means can be re-programmed with time vending units via further signals adapted to be received by the receiver means and/or the pickup means. In accordance with a fourth aspect of the present invention there is disclosed a transmission arrangement adapted for use with the system of the second aspect, in which the transmission arrangement is configured to transmit the time vending signal. In accordance with a fifth aspect of the present invention there is disclosed a headset assembly comprising an electrical connector housing, transducers for reproducing audio signals received at said connector, and a non-volatile memory means arranged in said housing and adapted to enable and disable reproduction of said signals by said transducers. In accordance with a sixth aspect of the present invention there is disclosed a vending machine adapted for the re-programming of time vendible units within the headphone means of the first aspect or the headphone assembly of the fifth aspect.

In accordance with a seventh aspect of the present invention there is disclosed a time vending signal distribution system in accordance with the first aspect in which the source is adpated for access and control by the user of the receptor unit, the source further comprising information pre-recorded in combination with time vending signals on permanent or semi-permanent recording media and means for reading and sending said pre-recorded information and time-vending signals to said receptor unit. Preferably the information and time-vending signals are encrypted and the receptor is equipped to decrypt said signals. Generally, the recording media can be an audio or video tape or disc, a computer data or program disc or solid-state memory or the like. The recorded media can be purchased, rented or obtained free by the user through any appropriate distribution system.

In accordance with an eighth aspect of the present invention there is disclosed a time vending signal distribution system in accordance with the first aspect in which the source includes means to compress or expand the time scale of the signal distribution and the receptor includes means to conversely expand or compress the time scale of the received signals. The expansion or compression means includes memory for storage of information and time vending signals, the time vending signals operating to control the time unit value in real time. Preferably the information and time vending signals are digital in nature and can be encrypted. This aspect is applicable, for example, to cable or satellite television transmission and can enable the reception of information and time vending signals of one programme while reproducing information signals of another programme with corresponding time vending control. Brief Description of the Drawings

A number of preferred embodiments of the present invention will now be described with reference to the drawings in which:

Fig. 1 shows a schematic block diagram representation of one embodiment of the present invention; Fig. 2 illustrates a configuration according to the embodiment of Fig. 1;

Fig. 3 shows an alternative configuration permitting remote induction and/or reception;

Fig. 4 illustrates a time vending machine; Fig. 5 is a schematic block diagram representation of a multi-channel audio distribution system of another embodiment;

Fig. 6 is a schematic block diagram representation of the line driver of Fig. 5;

Fig. 7 is a schematic block diagram representation of the headset drivers of Fig. 5;

Figs. 8A and 8B are respectively perspective and block diagram representation of the headset assemblies of Fig. 5.

Fig. 9 is a schematic block diagram representation of a signal distribution system of the preferred embodiment; Fig. 10 depicts an arrangement of the transmission network;

Fig. 11 is a timing diagram for coding in Figs. 9 and 10;

Fig. 12 is a schematic block diagram representation of the preferred embodiment of the personal receiver unit of Fig. 9; and

Fig. 13 is a circuit schematic of the receiver/transmitter of Fig. 12.

Best and Other Modes for Carrying Out the Invention

Referring to Fig. 1, a time vending audio distribution system 10 is shown which includes a transmission system 20 and a headphone assembly 30. The transmission system 20 can be formed within an interior cabin lining 22 of a structure such as an aircraft, coach or rail carriage. Also, fixed structures such as office blocks, railway platforms and the like can be built or modified to incorporate the system 20. Preferably, a transmission conductor 24 is arranged to run behind the lining 22. Spaced apart on the conductor 24 are a plurality of electromagnetic inductors 26, of which only one is shown illustrated in Fig. 1 for clarity. The inductors 26 permit electromagnetic coupling of a modulated carrier signal, transmitted over the conductor 24, through the cabin lining 22 for reception by the headphone assembly 30.

The electromagnetic inductor 26 can be provided as one half of an E-core or a potcore transformer for example which is positioned immediately behind the lining 22. In this manner, the lining 22 represents a flat, substantially vandal-proof surface through which electromagnetic coupling of sound di tribution signals can be made.

The headphone assembly 30 includes an inductive pickup 32 electrically complementing the inductor 26 and which can be positioned near and/or affixed to the lining 22 using a magnetic or suction arrangement as known in the art. Other arrangements such as clips, hooks and/or slotted keyways can also be used. In this manner, the inductor 26 and pickup 32 together form an electrical transformer for the coupling of the modulated carrier signal through the lining 22 and into the headphone assembly 30. The inductive pickup 32 firstly connects via a direct connection 34 to a power supply 36 which rectifies AC signals induced into the pickup 32 and thereby can supply power to the remaining components of the headphone assembly 30. The power supply connections to the remaining components are not shown illustrated in the drawing, as they are known to those skilled in the art.

In this specification, audio signals are deemed to be any signal below 20 kHz, and any signal having a frequency greater than 20 kHz, such as those used for modulation purposes, is deemed to be a radio frequency (RF) signal. The inductive pickup 32 is also adapted to receive RF signals and connects to an RF amplifier/filter 40 via a further connection 38 which permits a decoupled interconnection between the pickup 32 and the RF amplifier/filter 40. This permits the latter to be powered by the power supply 36 yet permitting maximum sensitivity to signals received by the pickup 32.

In the preferred embodiment, the system 10 is configured for the distribution of sound having a voice bandwidth of between about 200 Hz and about 3,000 Hz. In this manner, audio signals can be transmitted over the conductor 24, for example using frequency modulation (FM), with a carrier frequency of approximately 60 kHz. Using various modulation techniques known in the art, multiple audio channels can be supplied over the conductor 24 all based about a single carrier frequency.

Accordingly, the RF amplifier/filter 40 is configured to have a bandpass function centered about the carrier frequency and having a bandwidth suited to that of the modulated frequency. The RF signal is then passed to a detector/demodulator 42 which demodulates those signals transmitted with the carrier frequency. The demodulator 42 includes a baseband output 44 configured to output a baseband audio signal having a bandwidth of between about 200 Hz and about 3,000 Hz. The baseband output 44 supplies, via a volume control 58, a phone amplifier 54 permitting acoustic preproduction by a headphone transducer 56. The demodulator 42 also provides an auxiliary band output 46 to an audio/tone detector 48 which is configured to detect time pulses or control tones transmitted at periodic intervals over the transmission conductor 24. When a pulse or tone is detected, the detector 48 outputs a signal to a microprocessor timing memory control unit 50. The unit 50 includes an E PROM or non-volatile RAM memory, and supporting microprocessor logic which permits preprogramming of the memory with a number representing time vending units of sound reception purchased by the user. Upon receiving a detected tone or pulse from the detector 48, the time unit value in the memory is decremented by one. In this manner, the headphone assembly 30 can be configured to operate for a predetermined period of time when connected to receive audio signals. When the credited time vending units stored in the E^PROM are decremented to zero, the logic functions of the control unit 50 enable a switch 52 which disables the phone amplifier 54 thereby preventing acoustic reproduction of transmitted signals by the headphone transducer 56. In this manner, once the preprogrammed time allocation has been expired, the headphone assembly 30 is no longer operable for the reproduction of audio signals.

Turning now to Fig. 2, one configuration of the system 10 of Fig. 1 is shown. A ducting 60 is arranged suspended from a ceiling (not illustrated) and carries the modulated carrier signal, either via electrical conductors, or by a waveguide configuration, as known in the art. The headphone assembly 30 is shown including a housing 62 connected to the headphone transducers 56 via a pair of leads 66. The housing 62 includes a connector surface 64 which connects to the ducting 60, by magnetism for example. The housing 62 includes all components of the circuit of the assembly 30 shown in Fig. 1, save for the transducers 51. The volume control 58 is also seen. With this configuration, the assembly 30 can receive induced electrical energy from the ducting 60 for use in powering its circuitry. In an alternative configuration, shown in Fig. 3, a headphone assembly 70 is shown in which the transducers 56 and leads 66 connect to. a control unit 72. The control unit 72 includes an RF antenna 74 adapted to receive RF transmissions substituting for the distributed (inductive) transmission system 20 of Figs. 1 and 2. In this manner, a small, unobtrusive transmit antenna can be arranged within the aircraft, train, coach, etc. to locally transmit programme audio signals for RF reception by an RF receiver (known in the art) arranged within the control unit 72. The control unit 72, can be powered by a battery source in a known manner. Alternatively and/or supplementally, a pickup similar to that in Fig. 1 can be provided to replace the antenna 74. The pickup in this embodiment is configured to receive programme audio signals and electrical energy remote from a source thereof, such as the ducting 60 of Fig. 2. An induction range of up to 3 metres is suitable. In this manner, the headphone means 70 is passive to the extent that it requires no physical connection to a transmission or power source.

Also seen in Fig. 3 is a carry case 78 for the control unit 72, leads 66 and transducers 56. A clip 80 can also be provided in the usual manner. In the embodiment of Fig. 3, time vending operation of the headphone assembly 70 is similar to that of Fig. 1. However, rather than receiving a time vending signal, a clock can be provided within the control unit 50 to decrement the preprogrammed time value. Alternatively, a counter can be incremented for comparison with the programmed time value. The clock or counter can be made operable based on the reception of audio signals (at the demodulator 42), or by the direct application of electrical power to the circuit, for example. When the time allocated by the vending units has expired, and the assemblies 30,70 are no longer operable, the headphone assemblies 30,70 can be inserted into an appropriately configured vending machine 90 such as that shown in Fig. 4. The vending machine 90 includes a display 91 (an LCD for example) which instructs the user as to the operation thereof. A bank note receiving slot 92 and coin slots 93 are arranged for the user to insert monies that enable time vending crediting of the headphone assemblies 30,70. The machine 90 has two operations and is divided into two halves 98 and 99 respectively for each operation. Both halves 98,99 include user input keys 94 which permit appropriate selections to be made on the respective half.

The half 99 is configured for the purchase and supply of the headphone assemblies 30,70 which exit an outlet 96 as shown, with the carry case 78.

The half 98 is configured for the vending of time units. The housing 62 (or control unit 72) is inserted into a receptacle 95 as illustrated in which an inductor or RF transmitter is configured. For example, the inductor complements the operation of the inductor 26 of

Fig. 1, and is configured to cause operation of the headphone assembly 30 for the preprogramming of the memory within the control unit 50. In this manner, the vending machine 90 can be configured to output a series of control signals which are demodulated by the demodulator 42, detected by the detector 48 and passed to the microprocessor control unit 50 for interpretation. Accordingly, the memory therein can be updated to a new value depending upon a particular value of monies inserted into the vending machine 90 by the user. After this operation, the headphone assembly 30 can then be recoupled to the transmission system 20 for operation as before.

Where the assembly 70, which is configured to receive RF signals, is inserted Into the receptacle 95, a complementary RF transmitter arranged therein is configured to re-programme the memory in the above manner. Returning to Fig. 1, in a further embodiment, the demodulator 42 can be provided with a user operable switch arranged to select any one of the number of transmission channels of signals broadcast by the system 20. For example, in a coach or airline environment, five channels can be provided which include four audio or music channels and one video channel, thus complementing television displays arranged throughout the cabin. Alternatively, a ducted transmission system such as that illustrated in Fig. 2, can have different sections arranged for the transmission of different programme material. For example, with reference to Fig. 2, the ducting 60 can include a number of colour coded sections 82,84 which are configured to transmit different programme material. The headphone assembly 30 can thereby be connected to the appropriate section 82,84 depending on the programme desired to be received.

Also, with such a configuration, various weights can be applied to the cost of receiving different programme material. For example, if the headphone assembly 30 is configured to receive video derived audio signals, the video-audio signals can be configured to provide a one time decrementing pulse every five minutes, for example. Alternatively, the standard audio channel signals can be configured to provide one time decrementing pulse every ten minutes. In this manner, the reception of standard audio channel material can be made at half the price of video channel material .

Programme source material for the transmission system 20 of Figs. 1 , 2 or 3 can be operated directly from a radio or television receiver, or from any pre-recorded medium such as CDR0M and tape sources such as video tapes and/or quality audio tape. Where a video tape system is used, a single high fidelity video cassette recorder can be used to provide five audio channels each having a bandwidth of at least approximately 3 kHz. In this manner, a single video tape can provide an entertainment source of one video sound channel and four standard "music" channels, having different time vending pulses if necessary. The video sound channel would complement a video image channel in the usual manner. Still referring to Fig. 1, preferably, each of the power supply 36, RF amplifier/filter 40, demodulator 42, detector 48, controller unit 50, switch 52, and amplifier 54 are formed as a single application specific integrated circuit which can be readily positioned within a housing of the headphone transducer 56. In this manner, the entire configuration of the headphone assembly 30 can approximate the same size as known headphone assemblies used with portable cassette recorders and the like. Generally, the headphone transducers 56 consume approximately 120 milliwatts of power and with low power integrated design, the remaining components of the assembly 30 consume between about 100 milliwatts and 2.5 watts depending on the type of construction. Accordingly, in the embodiment of Fig. 1, it is required that the inductive pickup 32 be able to extract appropriate levels of electrical power from the transmission conductor 24. In this sense, the provision of a high frequency modulated carrier assists in the construction of high efficiency, small size inductors 26 and pickups 32. For example, 1f a high fidelity audio bandwidth of 20 kHz were required, a carrier frequency of approximately 1. MHz to 2 MHz would be required. Such frequencies are conducive to the construction of small size, relatively high power transformers.

Furthermore, although the inductor 26 is shown in Fig. 1 to configure in parallel with the conductor 24, an alternative configuration is to arrange a plurality of inductors 26 1n series throughout the cabin. In this manner, direct interconnection of the Inductors 26 can reduce the capital cost of components.

In a further alternative, although the embodiment illustrated derives its power source directly from the transmission conductor 24, a battery backup can be provided which can interconnect with the power supply 36 1n a known manner to supply the remaining components. Turning now to Fig. 5, -time vending multi-channel audio distribution system 100 is shown which can be configured for use in aircraft, railway carriages and coaches for example. The system 100 includes a video cassette recorder 102 which acts as a source of video and audio signals and from which a video signal 106 can be displayed using a video display unit (VDU) 108. The VCR 102 is configured to output three audio channels 104 to a line driver 110 which distributes the audio signals to a plurality of headset drivers 150 distributed about the cabin of the plane, train or coach. Into each headset driver 150, two headset assemblies 190 can be inserted so as to enable the acoustic reproduction of a selected audio channel output from the VCR 102. The audio channels 104 generally comprise one audio channel complementing visual matter displayed on the VDU 108, and two further channels for speech and/or music. Preferably, the VCR 102 is a hi-fi VHS type device. With this configuration, the system 100 can provide users with the option of viewing and listening to video material displayed on the VDU 108, or to select one the of two audio channels.

Turning now to Fig. 6, the line driver 110 includes a DC input 112 for accepting, for example, 12 volt DC supply from the coach. For aircraft applications, a 400 Hz supply can be used. The input 112 is supplied to a DC-DC converter 114 which outputs a 24 volt DC output 116 capable of supplying 6 amps to the headset drivers 150. The converter 144 also provides 5 volt DC and 12 volt DC for other system operations. The 5 volt DC is used locally within the line driver 110 for logic operations, and the 12 volt DC is used locally within the line driver 110 as well as being supplied to the headset drivers 150 via the output 116.

A power monitor unit 118 monitors the voltage and current output from the converter 114 and provides over-voltage and over-current protection. The power monitor 118 outputs a test voltage signal 120 to a controlling microprocessor 122 which determines the state of power supplied by the converter 114 and outputs an enable/disable signal 124 permitting the switching off of the converter 114 in the event of a major fault. The line driver 110 receives the audio input 104 from the VCR 102 via a connector 126. The audio input 104 is shown as having channel components 104A, 104B and 104C. These are input to a series of line amplifiers 130. Also input to the line amplifiers 130 is a sleep channel signal 128D provided via a sleep channel generator 128. The sleep channel generator 128 uses digital audio synthesis to create a soothing simulation of sea/surf sounds which are applied to the line amplifiers 130 thus permitting a further audio channel to be distributed to the headset drivers 150. The sleep channel signal 128D can assist persons to sleep whilst muffling out extraneous noi es from the plane, train or coach. The line amplifiers 130 output four audio output signals 134A, 134B, 134C and 134D to a connector 136.

The microprocessor 122 monitors the audio signal level of each of the inputs 104A, 104B, 104C and 128D by means of an analog-to-digital converter integral within the microprocessor 122. Whilst audio signals are present, the microprocessor 122 can output an interrupt request signal 140 to each of the headset drivers 150 in the system 100 so as to activate a time decrementing process within each headset driver 150 to permit time vending of signals sourced from the VCR 102. When no audio levels are present, the time decrementing function is disabled. The microprocessor 122 can also receive information from the headset drivers

150 by means of a pulse input line 138. Turning now to Fig. 7, each headset driver 150 includes a connector

151 which can be mated with the connector 136 for receipt of the audio signals 134 output from the line driver 110. The headset driver 150 is configured to provide audio outputs for two headset assemblies 190 and, accordingly, includes two pipelined circuits which operate in parallel for supplying signals to each headset assembly 190.

The headset driver 150 includes a controlling microprocessor 152 which connects to the pulse line 138 and interrupt request line 140 of the line driver 110. The microprocessor 152 also interconnects, via a keypad scan logic circuit 154 to a keypad 156 which permits a user of a headset assembly 190 to select one of the audio channels and control the audio output level. The microprocessor 152 sequentially applies continuous digital codes to the keypad scan logic 154 via key address scan lines 153. Each code applied to the keypad scan logic 154 causes one sensor of the keypad 156 to be connected via interconnecting lines 157, through the keypad scan logic 154 to the microprocessor 152 via a key detect line 155. If a keypad sensor is contacted by the finger of a user, the state of the key detect line 155 will change to a logic state which will indicate to the microprocessor 152 that the key, whose code is present on the key address scan lines 153 is active. The microprocessor 152 uses this code to identify which key has been activated. The keypad 156 permits channel selection and level control as will be described.

The audio input lines 134 connect directly to two channel switching circuits 158a and 158b which operate for the two outputs of the headset driver 150. The channel switching circuits 158a,b are provided with channel select signals 160a,b which permit selection of one channel 162a,b of the four channels 134 input to the headset driver 150. The selected channel 162a,b is input to a level control unit 164a,b. Level control signals 166a,b are output from the microprocessor 152 to control the level of the selected channel using the level control circuit 164,b. The level control signals 166 are determined as a result of a user depressing the keypad 156.

After level control, the selected channel signal 162a,b is input to a pre-amplifier and synthesizer 168a,b which converts a monoaural source signal from the VCR 102 into a pseudo-stereo signal 170a,b. The audio signal is split by means of active filters within the synthesizer 168a,b into two discrete audio channels each comprising separate audio spectrum products to provide a realistic simulation of a true stereo signal. This is then applied to a power amplifier 172a,b and then to a corresponding headset socket 174a,b. Also connected to the headset socket 174a,b is an I/O data line 176 which permits data flow to and from the headset assemblies 190 (as will be described), as well as a data clock signal 178.

Directly interconnecting the microprocessor 152 and the headset socket 174a is a chip select line 180, and similarly, a chip select line 182 directly connects the microprocessor 152 with the headset socket 174b. Turning now to Figs. 8A and 8B, a headset assembly 190 is shown which comprise an edge connector 191 that is insertable into the headset sockets 174a or 174b. The edge connector 191 is mounted from a housing 198 which encloses an EEPROM 192, and includes a connecting I/O data line 194, data clock line 195, and chip select line 196 complementing the functions of the lines 176, 178, 180 (or 182) as shown in Fig. 7. Also extending from the edge connector 191 are leads 197 which connect to two headset transducers 193 in the usual manner. With this configuration, the EEPROM 192 can be used to store digital coding data which is used to determine the available time for use of the particular headset assembly 190. When audio levels are present on the signal monitoring lines 132 (see Fig. 6), time decrementing for headset use is activated so that when a headset assembly 190 is plugged into a socket 174, the microprocessor 152 of the corresponding headset driver 150 is able to test the memory contents of the EEPROM 192 to determine if the contents of the EEPROM 192 represent a value which permits that headset assembly 190 to receive audio signals. If the digital code represents an expired value, reproduction of audio signals is not permitted. This is obtained through disabling the operation of the keypad 156 and zeroing the level control 164 of the corresponding socket 174. If the contents of the EEPROM 192 represent available usable time, the level control 164 is enabled and the microprocessor 152 periodically decrements the digital code within the EEPROM 192. When the code reaches the value represented by the expiry of available time, the microprocessor 152 sets the level control 166 to a minimum value thereby disabling the reproduction of audio signals via the headset 193.

It will be apparent from the foregoing that the system 100 permits time vending of signals in a hard-wired distributing system merely through the emplacement of an EEPROM 192 within a headset connector 198,191. In this manner, as with the earlier embodiments, a user of the headset assembly 190 can insert the connector 191 into an appropriately configured vending machine so as to reinitialise the contents of the EEPROM 192 to a new value thereby permitting re-use of the headset assembly 190.

Also, the time vending distribution system can be used in RF systems such as standard radio and television broadcasting, or GPS satellite navigation systems. In these applications, the receiver is configured to receive the broadcast signal which includes an encoded receiver designator number followed by a time unit value. The receiver designator number identifies the receiver which permits receipt of the following time unit value which can be stored. When the time unit value is valid, reception of normal signals is permitted which include a time vending signal which decrement the unit value. When the unit value is zero, the reproduction of normal signals is disabled.

The user of the receiver can purchase time units by paying an account for a set number of units. Once the account is paid, the transmitter is enabled to transmit the appropriate receiver designator number and time unit value.

It will be apparent that the foregoing system can be supplemented ^' by encryption to ensure that unauthorised users cannot gain access to transmitted information. Accordingly, a cost effective alternative to cable television is able to be implemented. Fig. 9 depicts a time vending signal distribution system 200 of the preferred embodiment. The system 200 includes a vending system 202 which is configured to dispense time units of signal reception whϊcfi enable useful operation of a personal receiver unit 220. The vending system 202 further supplies receiver units 220, batteries and/or time unit energy cells which comprise a purpose built battery that is configured to supply electrical energy to a personal receiver unit 220 for a predetermined period of time prior to self-disablement. The vending system 202 can be a vending machine in the manner earlier described, an over-the-counter sales outlet, or any other appropriate sales system. Time units are dispensed from the vending system 202 by a secure two-way transmission between the vending system apparatus and the personal receiver unit 220 in response to user instructions and in exchange for a specified payment or credit transaction. Alternatively, time units can be dispensed from the vending system 202 in a non-volatile memory capsule which can include a security arrangement, the capsule being insertable into the receiver unit 220 to enable its operation. Those skilled in the art will appreciate that a particular monetary exchange is not essential in that, for example, in an over-the-counter sales outlet, time units may be dispensed free of charge in return for other goods and/or services purchased by the user.

A preferred method of transmission for dispensing time units is by close-coupled radio frequency transmission to a signal receptor 222 in the receiver unit 220. In such an arrangement, the receptor 222 is, in this mode, adapted to function as an RF emitter (to be later described). The distribution system 200 includes a programme source 204 which can be supplied from a video tape which can provide up to 5 audio channels having a bandwidth in excess of 3 kHz. Other pre-recorded media such as compact audio discs and CD ROM can be used. Broadcast media such as radio and television transmissions can also be sourced. Time unit decrementing pulses can be pre-recorded on each audio channel within a recording medium such as video tape such that separate channels attract a different rate of charge. Alternatively, included within the reproducing device (e.g. VCR, compact disc player), additional circuitry can be provided to inject the time decrementing pulses into the audio video programme signal .

The programme source 204 outputs to an encryption system 206 which acts to combine time vending codes with the audio signals to produce unitary signals for each audio channel. Such an arrangement acts to encrypt the audio signals to prevent unauthorised reception thereof. The time-decrementing codes can be set by pre-loaded decrementing rates. Generally however, they are set by intercepted tone bursts derived from the programme source 204. The tone bursts are generally filtered from the signal prior to transmitting the combined signal. The encryption system 206 is preferably microprocessor based with on-chip security programming thereby making such an arrangement security upgradable.

Code "keys" are combined with the audio signals for transmission to the receiver units 220 where they are processed by a stored decryption programme. The encryption system 206 outputs to a sender unit 208. The unit 208 is generally an audio power amplifier for hardwired transmission systems, but otherwise can be a modulated RF generator of an appropriate type (AM, FM, Multi-channel, frequency hopping or spread spectrum).

The sender unit 208 couples to an appropriate transmission system 210 which can be either hardwired, close inductive or capacitive coupling, reactive electric or magnetic near-field systems, or radiated . electric or magnetic far-field systems. Near-field transmission relates to where the distance of transmission is substantially less than l/2π wavelengths. For example, for a transmission frequency in the 3-4 MH∑ range, a significant advantage can be gained from using the "near field" mode of transmission up to a range of about 3 to 4 metres. Also, infra-red or optical fibre transmission arrangements can be used.

The personal receiver unit 220 includes a receptor 222 configured depending upon the type of transmission system 210 used in the distribution system 200. For example, the receptor 222 can comprise a wired connector and associated amplifier for hard-wired systems. Alternatively, an electric or magnetic (e.g. ferrite rod) RF antenna with RF amplifier and receiver can be provided. Inductive or capacitive clamp-on or magnetic holding pick-ups can be used with the non-wired systems indicated above. Carrier channel selection can also be included, which can be controlled by a decryption system 224 or other controlled circuitry (not shown illustrated).

The decryption system 224 operates to demodulate time decrementing pulses as well as providing system security. A simple time-decrementing system has only filters and/or logic to separate time-decrementing signals from audio signals, together with an appropriate control programme to decrement a time unit store 230 and interrogate the store 230 to determine its status. Audio reproduction is inhibited when the status of time units retained in the store 230 has been exhausted. A secure transmission system has a combined time-decrementing and programme decryption arrangement carried out by a microprocessor, for example, according to transmitted code data and a local microprocessor programme. Decryption can be inhibited when the time units retained in the personal receiver unit 220 are exhausted. Such an arrangement can al o be supplemented by enabling the reception of unencrypted signals when the time units are exhausted. Such an arrangement is advantageous to enable purchasing of time vending units.

If the received signals have been encrypted using frequency-hopping or other frequency agile techniques, or spread spectrum techniques, the decryption system includes frequency synthesiser control circuitry which can advantageously manipulate the operation of the receptor unit 222. The secure time unit store 230 retains the time units in a non-volatile memory such as EEPROM, or RAM rendered non-volatile by means, of a battery backup. The non-volatile memory can be part of a decryption integrated circuit, or a discrete circuit element, or a removable capsule as earlier described. For secure operation, the time unit store is configured to be accessible only through the use of a security protocol. The decryption system outputs to a user system 226 which is configured to utilize the programme signal (e.g. video, audio, or data) supplied from the source 204. The user system 226 generally operates a device 228. Accordingly, the user system 226 and device 228 can be embodied in a wide variety of devices such as sound reproducing arrangements including electro-acoustic transducers, video displays, computer equipment, control devices for remote machinery operation and the like. For example, the system 200 can be configured to replace coin mechanisms in gas or hot water heating arrangements which are often used in tenancy situations.

In the preferred embodiment, the user system 226 is an audio system which comprises amplifier circuitry and volume control. The volume control can be a potentiometer arrangement whilst push button digital control using pulse width modulation may be preferred. The audio system can also include de-emphasis for the processing of demodulated FM signals. The audio system can be either mono or stereo depending on the level of processing required. Furthermore, stereo simulation circuitry can be incorporated for generating stereo-like sounds from mono transmissions- The audio system outputs to a headset assembly which occupies the role of the device 228 in Fig. 9. The headset assembly is generally a light-weight, low cost headset as currently used for in-flight movies and the like. However, head set type is not restricted and other transducers may be used such as those including loudspeakers, either with or without an auxiliary amplifier.

In one embodiment the programme source 204 and encryption system 206 can be incorporated with a time of transmission compression or expansion arrangement which permits for example the compressed time transmission of the source signal. In this manner, a feature length video transmission can be broadcast not in for example 120 minutes but rather 12 minutes using a 10:1 compression ratio. A higher transmission rate would however be required as would be appreciated by those skilled in the art. With such a transmission arrangement, a complementary reception arrangement is required in the personal receiver unit 220.

In one embodiment the receptor 222 can include a tape recording apparatus onto which the compressed transmitted signal is recorded (e.g. in 12 minutes) and from which play-back in real time can be performed (over 120 minutes).

In a further embodiment of the system 200, the programme source 204 can be configured on a medium, such as a computer memory, compact disc or cassette tape which can be sold at nominal or nil cost, but for which time valued re-play is required. As before, the information signal is encrypted together with a time vend signal for which appropriate decryption is required in the personal receiver unit 220, which can incorporate a complementary medium play-back device for the computer memory, compact disc or cassette tape. Fig. 10 shows one possible arrangement for the transmission of signal in Fig. 9. Four audio input lines 242-245 are supplied to a multiplexer 248 which acts to switch each of the audio line inputs 242-245 to one of a corresponding number of radio frequency transmitters 250 each of which connects to a common transmit antenna 254. The individual transmitters 250 are arranged to transmit on separate carrier- frequencies thereby making available each of the four programme sources at any one time. The multiplexer 248 is controlled by a switching controller 258 which is input with an encryption code 256. The encryption code 256 acts to continually switch each of the four line inputs 242-245 amongst the four transmitters 250 in a pseudo-random manner.

Fig. 11 shows an arrangement of the encryption code 256 which is arranged in frames 282 preferably having a duration of one second. Within each frame 282 are arranged sixteen tone burst pulses preferably at 8192 Hz, which comprise a reference pulse 180 which has a predetermined pulse width and is arranged at the start of each frame 282. Following from the reference pulse 280 are a further fifteen pulses 284, 285, 286 ..., each of varying pulse width which represents the actual encryption data of the code 256. Each frame 282 of the encryption signal 256 is stored within the switching controller 258 whilst simultaneously being transmitted by each of the transmitters 250. As seen in Fig. 10, the transmitted signal is received by a radio frequency receiving antenna 260 which is arranged within the personal receiver unit 220 and which supplies four radio receivers 262. The receivers 262 are arranged to complement each of the transmitters 250 and demodulate the signals transmitted therefrom. These signals are supplied to a demultiplexer 268.

The encryption code 256 is arranged in the frames 282 so that the code within any one frame is transmitted for reception by the personal receiver unit 220 whereby it is decoded from the demultiplexer 268 and input into a switching controller 270, which operates to control the demultiplexing of the demultiplexer 268. In this manner, the code transmitted in any one frame represents the decrypting code for the next, or a subsequent, frame.

The preferred implementation of the distribution system 200 utilises narrow band FM radio frequency transmission having a maximum radiated field strength of 43 dBμV/m at a range of 3 metres from the antenna. Such an arrangement has been found to be desirable for an implementation within a rail carriage.

The preferred implementation of the personal receiver unit of such an application is shown in Fig. 12 where a personal receiver unit 300 includes an antenna 302 which connects to an RF amplifier 304 which in turn supplies a mixer 306. As opposed to the configuration shown in Fig. 10 where four separate radio receivers 262 are shown, the arrangement illustrated in Fig. 12 represents a more cost effective manner of receiving a frequency hopping signal in which the local oscillator is switched so as to provide mixing sufficient to demodulate the four carrier frequencies respectively.

The mixer 306 outputs to an IF amplifier 308 which comprises several stages in cascade, with an overall gain sufficient to cause limiting of the output IF signal to occur even with the lowest working level of the RF input. The amplifier stages are designed to limit progressively to ensure consistent behaviour with all signals up to the highest level anticipated.

The IF amplifier 308 outputs to an FM detector 310 which is a standard quadrature demodulator, having an LC tuned-circuit phase-shifter and balanced transistor phase detector. An RC filter is incorporated to remove components at twice the IF. The FM detector outputs to a notch filter 312 which is a third- order low pass filter with a transmission zero at 8192 Hz, the sub-carrier of the code signals used for decryption. The filter prevents audible interference by the codes.

The notch filter 312 outputs to a volume control 314 which can be a conventional potentiometer whilst, in the preferred system, a high frequency pulse width modulation of the audio signal under microprocessor control is used. This permits volume control by up and down keys on a keypad 336.

The volume control 314 outputs to a de-emphasis unit 316 which comprises a single RC time-constant that corrects the frequency pre-e phasis of the transmitted audio signal and simultaneously filters high frequency components generated by the pulse width modulated volume control 3 and 4.

The de-emphasis unit 312 outputs to a stereo simulator 318 which acts to replicate the input audio signal but delayed by 0.5 milliseconds. The delayed signal is then added to the original signal to generate one audio channel signal, and subtracted from the original signal to generate the other audio signal. The delay is achieved by a clocked switched-capacitor technique. The simulator 318 outputs to a pair of audio amplifiers 320 which have a bandwidth of about 6 kHz and output to a low cost 32 ohm headset unit 322.

The RF amplifier 304 is supplied by an RF tuning circuit 324 which is a microprocessor controlled analogue switch, enabling dynamic selection of a suitable antenna-loading capacitor to be performed when frequency hopping, or static selection when not.

The mixer 306 is supplied from a frequency synthesiser 326 which comprises a local oscillator signal generated by a pair of phase-locked loop circuits with a common reference frequency of 16384 Hz. The division ratio of each loop is controlled by a microprocessor 334. The use of two loops instead of one allows time for either one of the loops to stabilise before being connected to the mixer 306. When frequency-hopping, the interval between hops is preferably 1/16th of a second. The phase detector in each loop is of a type that is also frequency sensitive to generate locking in any hop range. A crystal time base 328 is provided which comprises a 32768 Hz Colpitts oscillator using a common watch crystal as the reference. Dividers are provided to enable generation of other timing signals which are used throughout the receiver unit 300.

The FM detector 310 outputs to a tone detector 330 which comprises a phase tracking detector synchronised to an 8192 Hz clock signal with quadrature drive phases. This provides for high selectivity, fast response and low cost. An equivalent band pass response is provided by two low pass RC ladder filters acting on the detected outputs.

The RF amplifier 304 is operable either as a receiver or as a transmitter using the same antenna 302 in either mode. As shown in Fig. 13, a single transistor 350 can perform either task without changing its circuit connection. When receiving, the transistor 350 operates in common-base mode, wherein a signal supplied by the antenna 302 to the emitter is amplified and output to an RF transformer 351 connected to the collector. When transmitting, the transistor 350 effectively operates in common-collector mode, wherein a signal supplied to the base by a microprocessor-controlled switching driver 352 is amplified and output from the emitter to the antenna 302. No use is made of the collector output in the transmitting mode. Preferably, the switching driver 352 provides a static low-impedance AC signal path to ground at the base of the transistor 350 during signal reception, for optimum performance of the amplifier 302. An arrangement of resistors 353-356 are provided to ensure appropriate biasing of the transistor 350 in each of the modes. A capacitor 357 can be used to provide for tuning the amplifier 305 when in the receiving mode, and enhancing the common-collector arrangement when transmitting at a different frequency to that of the receiving mode.

The personal receiver unit 300 operates from a battery supply and includes a battery monitor 332 which detects a low battery condition and an indication of which is provided to the microprocessor 334 which is arranged to generate a regular warning signal that is injected into the volume control circuit 314. Such a signal can be heard by the user of the headset 322 who is alerted to rectify the low battery condition. Under control of the momentary channel-select, or volume change key on the keypad 336, the microprocessor 334 computes the required synthesiser and timing data and sends control data to the respective units 324,326.

The keypad 336 comprises an el stomeric switch assembly with contact pads on a printed circuit board. The pad includes four channel buttons, an OFF button, and two volume control buttons, activation of any channel key automatically turns the receiver "on".

Interconnected to the microprocessor 334 is a ROM device 338 which, in conjunction with other hard-wired logic, the ROM 338 stores essential code for determining basic operation of the receiver without encrypted signals.

A RAM 340 is provided to store the most security sensitive decryption code which is volatile if the main battery is removed for more than the time needed for a simple battery replacement (temporary supply storage is provided by a capacitor connected to the RAM 340).

A non-volatile (NV) RAM 342 is provided and has its data retained by a silver oxide backup cell inserted at the time of manufacture of the receiver 300. During the manufacturer's test, certain code is entered into the NV RAM 342 which enables communication with the vending machine 202. The count of available time units is also stored in the NV RAM 342. Provision is made in the receiver 330 to establish security locks in the microprocessor 334 to protect data in certain areas of the RAM 340 and NV RAM 342 from being read out or corrupted. The security locks can only be reset by clearing all data from the memory at the same time. The memory is organised on the principle that volatile data is the most secure from unauthorised reading as it is only present in the form of minute charges. ROM data is defined in interconnection patterns on the silicon chip and can therefore be read under a microscope, albeit it with difficulty. The physical construction of the receiver 300 is preferably configured such that the exterior case cannot be opened without causing damage to the circuit and without causing both the main and backup battery supplies to become disconnected, destroying all sensitive data. Most preferably, all memory is integral with the microprocessor device 334, thereby preventing direct access thereto.

The foregoing describes only a number of embodiments of the present invention and, modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention. For example, although some embodiments utilise inductive coupling, other remote coupling forms such as capacitive coupling can be used.

Furthermore, although monoaural transmission is depicted in some embodiments, the application of standard modulating and demodulation technology can permit the reproduction of stereo source material. Industrial Applicability

The present invention finds application in signal distribution systems for which a charge for supply of a signal is desired.

Claims

CLAIMS :

1. A signal distribution system comprising: a supply arrangement configured to provide a signal derived from a source: and at least one receiver unit adapted to receive said signal, said receiver unit comprising: a time unit store for storing a time unit value derived from time unit dispensing system; control means for reading the time unit value and if the valu is greater than a predetermined amount, reception of said signal is enabled; and update means for varying the time unit value.

2. A system as claimed in claim 1, wherein said control means includes a clock means arranged to periodically vary the time unit value.

3. A system as claimed in claim 2, wherein said clock means is enabled by reception of said signal by said receiver unit.

4. A system as claimed in claim 2, wherein said clock means is enabled by application of electrical energy to operate said receiver uni

5. A system as claimed in claim 1, wherein said supply arrangement is configured to provide a time variation signa.l which, when received by said receiver unit, is supplied to said update means for varying the time unit value.

6. A system as claimed in claim 1, wherein said signal comprises a programme information signal selected from the group consisting of audio signals-, video signals and data signals.

7. A system as claimed in claim 6, wherein said signal further comprises a time variation signal which, when received by said receiver unit, is supplied to said update means for varying the time unit value.

8. A system as claimed in claim 7, wherein said programme information signal and said time variation signal are separately supplie from and received by said supply arrangement and said receiver unit respectively.

9. A system as claimed in claim 7, wherein said programme information signal, and said time variation signal are combined for supply as a unitary signal, and said receiver unit comprises a receiver means for separating said programme information signal and said time variation signal from said unitary signal.

10. A system as claimed in claim 1, wherein said variation is either an increment or decrement of the time unit value.

11. A system as claimed in claim 10, wherein said variation represents a single or predetermined multiple of a base unit of the time unit value.

12. A system as claimed in claim 1, wherein when said reception is enabled, said receiver unit operates to provide a useful output therefrom.

13. A system as claimed in claim 12, wherein said useful output comprises a control signal adapted to control apparatus connected to said receiver unit.

14. A system as claimed in claim 12, wherein said useful output comprises said signal which is output to a reproducing device.

15. A system as claimed in claim 14, wherein said signal comprises an audio signal and said reproducing device comprises an electro-acoustic transducer means.

16. A system as claimed in claim 15, wherein said electro-acoustic transducer means comprises a headphone transducer.

17. A system as claimed in claim 16, wherein said receiver unit is configured as part of a headphone assembly including said headphone transducer.

18. A system as claimed in claim 14, wherein said signal comprises a video signal and said reproducing device comprises a video display unit.

19. A system as claimed in claim 13, wherein said signal comprises a data signal and said apparatus comprises a computer device arranged for processing data transmitted in said data signal.

20. A system as claimed in claim 1, wherein said supply arrangement comprises physical communication between said source and said receiver unit.

21. A system as claimed in claim 20, wherein said physical communication is selected from the group consisting of an electrical conductor arrangement, and an optical fibre arrangement.

22. A system as claimed in claim 1, wherein said supply arrangement comprises non-physical communication between said source and said receiver unit.

23. A system as claimed in claim 22, wherein said non-physical communication results from emissions selected from the group consisting of infra-red light transmission, electric induction, magnetic induction, near-field radio frequency emissions, and far-field radio frequency emissions.

24. A system as claimed in claim 1, wherein said source and said supply arrangement are selected from the group consisting of:

(i) a video tape and a video tape player; (ii) a compact disc and a compact disc player; (iii) a compact cassette and a compact cassette player; (iv) a digital audio tape and a digital audio tape player; (v) a computer memory and a computer device; and (vi) a transmitted signal and transmitted signal receiver, respectively.

25. A system as claimed in claim 20 or 22, wherein said supply arrang ent comprises a system configured to transmit said signal about a structure selected from the group consisting of an aircraft, a railway carriage, a multi-passenger motor vehicle, and a building.

26. A system as claimed in claim 20 or 22, wherein said supply arrangement comprises a transmission system arranged for simultaneous distribution of said signal from said source to a plurality of said receiver units at a plurality of different locations.

27. A system as claimed in claim 26, when dependent on claim 20, wherein said transmission system is selected from the group consisting of a publicly switched telephony network and an unswitched network.

28. A system as claimed in claim 26, when dependent on claim 22, wherein said transmission system is selected from the group consisting of a radio broadcasting network, a television broadcasting network, a satellite broadcasting network, and a cellular telephone network.

29. A system as claimed in claim 1, wherein said source and said supply arrangement form part of said time unit dispensing system, said dispensing system comprising a receptacle for emplacement of said receiver unit, said source comprising a currency receiving means for receiving a monetary credit provided by a user of said system, said currency receiving means determining from said credit a corresponding time unit value, said time unit value being output by said supply arrangement at said receptacle for communication of said time unit value to said receiver unit, said update means detecting reception of said time unit value and adding said time unit value received from said dispensing system to the time unit value in said time unit store, and retaining the added value in said store as an updated time unit value.

30. A system as claimed in claim 29, wherein said receiver unit further comprises a transmitter section and said time unit dispensing system includes a complementary receiver section thereby permitting two-way communication between said receiver unit and said time unit dispensing system.

31. A system as claimed in claim 30, wherein said transmitter section forms part of a transceiver means arranged both to receive said signal and transmit to said supply arrangement.

32. system as claimed in claim 31, wherein said transceiver means comprises a transistor having its emitter connected to a transmit/receive port of said receiver unit, its collector connected to a receive output of said transceiver means, and its base to a transmit input of said transceiver means wherein when enabled for reception, said transistor operates in a common-base mode, and when enabled for transmitting, said transi tor operates in common-collector mode.

33. A system as claimed in claim 32, wherein said transmit/receive port comprises a radio frequency antenna, said receive output comprises a tuned radio frequency transformer, and said transmit input comprises a switching driver configured to provide low-impedance path at said base when said transistor is enabled for reception.

34. A system as claimed in claim 29, wherein said time unit dispensing system is configured as a vending machine which dispenses said receiver units upon receipt of an appropriate monetary credit.

35. A system as claimed in claim 29, wherein said monetary credit comprises currency deposited into said currency receiving means.

36. A system as claimed in claim 29, wherein said currency receiving means includes a credit card reading device and said monetary credit represents funds debited against an account of a credit card inserted into said reading device.

37. A system as claimed in claim 1, further comprising encryption means interposed between said source and said supply arrangement for encrypting said signal, and said receiver unit includes a complementary decryption means having a decryption key for enabling reproduction of said signal .

38. A system as claimed in claim 31, wherein said encryption means comprises a code generator and a multi-path switch, said supply arrangement comprising a plurality of communication paths to said receiver unit wherein said code generator acts upon said switch to connect said source to one of said paths.

39. A system as claimed in claim 32, wherein said code generator acts to switch said signal through each of said paths in a pseudo-random manner.

40. A system as claimed in claim 39, wherein said code generator outputs a coding sequence comprising a reference component and a plurality of code components.

41. A system as claimed in claim 40, wherein said components are arranged in frames of predetermined duration commencing with said reference component, with the code- components of adjacent frames varying in said pseudo-random manner.

42. A system as claimed in claim 41, wherein said coding sequence is combined with said signal for transmission to said receiver unit whereby the code sequence for any one frame represents the sequence by which said switch selects said paths for a subsequent frame thereby enabling said receiver unit to receive the combined transmitted signal for said one frame, decrypt same to extract said coding sequence and using said coding sequence to connect said receiver unit to the corresponding communication paths for said subsequent frame.

43. A system as claimed in claim 42, wherein said subsequent frame is a next successive frame.

44. A system as claimed in claim 1, wherein said time unit dispensing system comprises a vending arrangement configured to dispense a non-volatile memory means including said time unit value upon receipt of a monetary credit provided by a user of the system.

45. A system as claimed in claim 44, wherein said memory means comprises a capsule insertable into said receiver unit to form at least part of said time unit store.

46. A receiver unit adapted for use with the system as claimed in any one of the preceding claims.

47. A time unit dispensing system adapted for use with the system as claimed in any one of claims 1 to 45.

48. A secure transmission system comprising a transmitting device and a receiving device, a plurality of communication paths between said devices by which at least one signal can be conveyed from said transmitting device to said receiving device, first switching means arranged in said transmitting device for switching said signal between said paths in accordance with a pseudo-random switching sequence and, a second switching means arranged in said receiving device for connecting said paths to an output thereof in accordance with said sequence.

49. A system as claimed in claim 48, wherein said first switching means comprises a switching controller which is input with an encryption code, said controller formatting said code into said sequence having a reference component and a plurality of code components.

50. A system as claimed in claim 49, wherein said components are arranged in frames of predetermined duration each commencing with said reference component, with the code components of each frame varying with said encryption code.

51. A system as claimed in claim 50, wherein said sequence is combined with said signal for transmission to said receiving device whereby said sequence for any one frame represents the sequence by which said first switching means selects said paths for a subsequent frame thereby enabling said receiver device to receive the combined transmitted signal for said one frame, decrypt same to extract said sequence, and using said sequence to operate said second switching means to connect said output to the corresponding paths for said subsequent frame.

52. A system as claimed in claim 51, wherein said subsequent frame is a frame immediately following said one frame.

53. A transceiver apparatus comprising a transistor having a first terminal thereof connected to a bidirectional transmit/receive port, a second terminal connected to a receive output, and a third terminal connected to a transmit input, wherein said transistor is operable in a first mode to accept receive signal at said first terminal and convey same to said second terminal, and a second mode to accept transmit signals at said third terminal and convey same to said first terminal.

54. A transceiver apparatus as claimed in claim 53, wherein said transistor is a bi-polar transistor having its emitter connected as said first terminal, its collector connected as said second terminal, and its base connected as said third terminal.

55. A transceiver apparatus as claimed in claim 54, wherein said first mode is a common-base mode and said second mode is a common-collector mode.

56. A transceiver apparatus as claimed in claim 55, further comprising a driver connected to said base for supplying said transmit signals thereto, said driver representing a static low impedance signal path when said transistor is operating in said common-base mode.

57. A transceiver apparatus as claimed in claim 53, wherein said bidirectional port comprises a radio frequency antenna, and said receive output comprises a radio frequency transformer.

58. A time vending signal distribution system comprising a source, and at least one receptor unit adapted to receive one or more information signals and a time vending signal output from said source, said receptor unit comprising a control means adapted to retain a record of a time unit value modified by said time vending signal, wherein said control means is adapted to use said time unit value to enable operation of said receptor unit to receive said information signals for a predetermined period of time to provide a useful output of said receptor unit.

59. A system as claimed in claim 58, wherein the time vending signal is integral with said Information signal.

60. A system as claimed in claim 59, wherein the information signal comprises a periodic time unit signal which is adapted to alter the time unit value to cause disabling of said receptor unit to prevent reception of said information signals after said predetermined period of time.

61. A system as claimed in claim 59, wherein the source is either a radio frequency (RF) transmitter, or a hard-wired distributed communication system and the receptor unit includes either a RF receiver or a device directly connectable to the distributed system respectively.

62. A headphone means comprising: reproducing means for reproducing a transmitted audio programme signal as an acoustic signal; and controller means adapted for programming with a user selected number of time vending units, said units being compared with a periodic time vending signal enabled through use of said headphone means such that said controller means disables said reproducing means when a time period of use equivalent to said units has been expended.

63. A headphone means as claimed in claim 62, wherein the audio program signal is transmitted either as a radio frequency signal, using magnetic induction, or through a distributed hard wired system.

64. A time vending audio distribution system comprising: a headphone means in accordance with claim 62; and transmission means arranged to transmit at least one said audio programme signal .

65. A system as claimed in claim 64, wherein the time vending signal is received by said headphone means as a signal integral with, or in addition to, said audio programme signal.

66. A system as claimed in claim 64, wherein the time vending signal is a clock signal internally generated within said controller means.

67. A system as claimed in claim 64, wherein the receipt of said time vending signal is used to decrement said units until a nil unit value is reached, or, to increment a counter for comparison with the programmed number of said units.

68. A system as claimed in claim 64, wherein the headphone means includes a pickup means adapted to receive energy transmitted by said transmission means and to convert same into electrical energy for the powering of said reproducing means and said controller means.

69. A headset assembly comprising an electrical connector housing, transducers for reproducing audio signals received at said connector, and a non-volatile memory means arranged in said housing and adapted to enable and disable reproduction of said signals by said transducers.

70. A vending machine adapted for the re-programming of time vendible units within the headphone means of claim 62 or the headphone assembly of claim 69.

71. A time vending signal distribution system as claimed in claim 58, in which the source is adpated for access and control by a user of the receptor unit, the source further comprising information pre-recorded in combination with said time vending signal on a recording media and means for reading and sending said pre-recorded information and time-vending signals to said receptor unit.

72. A system as claimed in claim 71, wherein said recording media is either permanent or semi-permanent.

73. A system as claimed in claim 71, wherein the information and time-vending signals are encrypted and the receptor unit is equipped to decrypt said signals.

74. A system as claimed in claim 71, wherein the recording media can be an audio or video tape or disc, a computer data or program disc or solid-state memory or the like.

75. A system as claimed in claim 74, wherein the recorded media is either one of purchased, rented or obtained free by the user through any appropriate distribution system.

76. A system as claimed in claim 58, in which the source includes means to compress or expand the time scale of distribution of said signal from said source and the receptor unit includes complementary means to expand or compress the time scale of the received signals.

77. A system as claimed in claim 76, wherein the expansion or compression means includes memory for storage of information and time vending signals, the time vending signals operating to control the time unit value in real time.

78. A system as claimed in claim 77, wherein information and time vending signals are digital are encrypted.

AMENDED CLAIMS

[received by the International Bureau on 1 September 1993 (01.09.93); original claims 1-78 replaced by amended claims 1-45 (6 pages)]

1. A time vending signal distribution system comprising: a source of one or more information signals and one or more time vending signals; at least one receptor unit adapted to receive at least one of said information signals and one of said time vending signals, said receptor unit comprising a time unit store configured to retain a record of a time unit value modifiable by said one time vending signal, and control means configured to examine said time unit value, whereby if said time unit value is greater than a predetermined amount, said control means enables operation of said receptor unit to receive at least one of said information signals for a predetermined period of time to provide a useful output of said receptor unit; and a time unit vending machine for initially dispensing said time unit value to said receptor unit.

2. A system as claimed in claim 1 wherein an initial value of said time unit value is related to a receipt of a monetary credit provided by a user of the system and results from a direct manipulation of said vending machine by said user.

3. A system as claimed in claim 1 wherein said time unit store comprises memory means integrally formed with said control means, and the dispensing of said time unit value results from two-way communication between said receptor unit and said vending machine.

4. A system as claimed in claim 1, wherein said time unit store comprises a non-volatile memory means dispensed from said vending machine and connectable by said user to said control means.

5. A system as claimed in claim 4, wherein said memory means comprises a capsule insertable into said receptor unit to form at least part of said time unit store.

6. A system as claimed in claim 1, wherein the time vending signal is integral with said information signal.

7. A system as claimed in claim 1, wherein said useful output comprises a data signal adapted to cause specific operation of a computer device connected to said receiver unit.

8. A system as claimed in claim 1, wherein said useful output comprises an audio signal output to a headphone transducer configured as part of a headphone assembly incorporating said receptor unit. 9. A system as claimed in claim 1, wherein said receptor unit is portable and configured to be carried by one single user of system, and said useful output is provided to said one user.

10. A system as claimed in claim 1, wherein said source comprises a supply system configured to transmit said signals about a structure selected from the group consisting of an aircraft, a railway carriage, a multi-passenger motor vehicle, and a building.

.11. A system as claimed in claim 10, wherein said supply system comprises a non-physical communication means providing emissions selected from the group consisting of infra-red light transmission, electric induction, magnetic induction, near-field radio frequency emissions, and far-field radio frequency emissions, said omissions propagating only within the vicinity of said structure for reception thereabout, said source further comprising any one of:

(i) a video tape and a video tape player;

(ii) a compact disc and a compact disc player;

(Hi) a compact cassette and a compact cassette player;

(iv) a digital audio tape and a digital audio tape player;

(v) a computer memory and a computer device; and

(vi) a transmitted signal and transmitted signal receiver, respectively, supplying an input of said non-physical communication means.

12. A system as claimed in claim 1, wherein time unit vending machine comprises a deposit means operable by said user for receiving said monetary credit, said deposit means determining from said credit a corresponding time unit value to that supplied to a non-volatile memory device which is then dispensed to said user.

13. A system as claimed in claim 1, wherein said time unit vending machine comprises a receptacle for emplacement of said receptor unit, deposit means operable by said user for receiving said monetary credit, said deposit means determining from said credit a corresponding time unit value, said time unit value being output by a supply arrangement at said receptacle for communication of said time unit value to said receptor unit, said control means detecting reception of said time unit value and adding said time unit value received from said vending machine to the time unit value in said time unit store, and retaining the added value in said store as an updated time unit value. 14. A system as claimed in claim 13, wherein said receptor unit further comprises a transmitter section and said supply arrangement comprises a complementary receiver section thereby permitting two-way communication between said receiver unit and said time unit dispensing system.

15. A system as claimed in claim 14, wherein said transmitter section forms part of a transceiver means arranged both to receive said signals and transmit to said supply arrangement, said transceiver means comprising a transistor having its emitter connected to a transmit/receive port of said receptor unit, its collector connected to a receive output of said transceiver means, and its base to a transmit input of said transceiver means wherein when enabled for reception, said transistor operates in a common-base mode, and when enabled for transmitting, said transistor operates in common-collector mode.

16. A system as claimed in claim 15, wherein said transmit/receive port comprises a radio frequency antenna, said receive output comprises a tuned radio frequency transformer, and said transmit input comprises a switching driver configured to provide low-impedance path at said base when said transistor is enabled for reception.

17. A system as claimed in claim 13, wherein said time unit vending machine is configured to dispense one of said receptor .units upon deposit of an appropriate monetary credit.

18. A system as claimed in claim 10, wherein said source further comprises encryption means preceding said supply system for encrypting said signals, and said receptor unit including a complementary decryption means having a decryption key for enabling reproduction of said signals, wherein said encryption means comprises a code generator and a multi-path switch, said supply system outputing to a plurality of communication paths to said receptor unit wherein said code generator acts upon said switch to connect said source to one of said paths in a pseudo-random manner.

19. A system as claimed i claim 18, wherein said code generator outputs a coding sequence comprising a reference component and a plurality of code components said components being arranged in frames of predetermined duration commencing with said reference component, with the code components of adjacent frames varying in said pseudo-random manner, wherein said coding sequence is combined with said signal for transmission to said receiver unit whereby the code sequence for any one frame represents the sequence by which said switch selects said paths for a subsequent frame thereby enabling said receiver unit to receive the combined transmitted signal for said one frame, decrypt same to extract said coding sequence and using said coding sequence to connect said receiver unit to the corresponding communication paths for said subsequent frame.

20. A system as claimed in claim 19, wherein said subsequent frame is a next successive frame.

21. A time vending signal distribution system as claimed in claim 1, in which the source is adpated for access and control by a user of the receptor unit, the source further comprising information pre-recorded in combination with said time vending signal on a recording media and means for reading and sending said pre-recorded information and time-vending signals to said receptor unit.

22. A system as claimed in claim 21, wherein said recording media is either permanent or semi-permanent.

23. A system as claimed in claim 21, wherein the information and time-vending signals are encrypted and the receptor unit is equipped to decrypt said signals.

24. A system as claimed in claim 21, wherein the recording media is one of audio disc or tape, video tape or disc, a computer memory disc, tape or solid-state memory.

25. A system as claimed in claim 24, wherein the recording media is either one of purchased, rented or obtained free by the user through any appropriate distribution system.

26. A system as claimed in claim 1, in which the source includes means to compress or expand the time scale of distribution of said signal from said source and the receptor unit includes complementary means to expand or compress the time scale of the received signals.

27. A system as claimed in claim 28, wherein the expansion or compression means includes memory for storage of information and time vending signals, the time vending signals operating to control the time unit value in real time.

28. A receptor unit adapted for use with the system as claimed in any one of the preceding claims.

29. A time unit vending machine adapted for use with the system as claimed in any one of claims 1 to 20. 30. A headphone assembly comprising: reproducing means for reproducing a transmitted audio programme signal as an acoustic signal; and controller means adapted for programming with a user selected number of time vending units, said units being compared with a periodic time vending signal enabled through use of said headphone means such that said controller means disables said reproducing means when a time period of use equivalent to said units has been expended.

31. A headphone means as claimed in claim 30, wherein the audio program signal is transmitted either as a radio frequency signal, using magnetic induction, or through a distributed hard wired system.

32. A time vending audio distribution system comprising: a headphone means in accordance with claim 30; and transmission means arranged to transmit at least one said audio programme signal.

33. A system as claimed in claim 32, wherein the time vending signal is received by said headphone means as a signal integral with, or in addition to, said audio programme signal.

34. A system as claimed in claim 34, wherein the time vending signal is a clock signal internally generated within said controller means.

35. A system as claimed in claim 34, wherein said clock signal is enabled by reception of said signal by said receiver unit.

36. A system as claimed in claim 34, wherein said clock signal is enabled by application of electrical energy to operate said receiver unit.

37. A system as claimed in claim 32, wherein the receipt of said time vending signal is used to decrement said units until a nil unit value is reached, or, to increment a counter for comparison with the programmed number of said units.

38. A system as claimed in claim 32, wherein the headphone assembly includes a pickup means adapted to receive energy transmitted by said transmission means and to convert same into electrical energy for the powering of said reproducing means and said controller means.

39. A headset assembly comprising an electrical connector housing, transducers for reproducing audio signals received at said connector, and a non-volatile memory means arranged in said housing and adapted to enable and disable reproduction of said signals by said transducers. 40. A time unit vending machine adapted for the re-programming of time vendible units within the headphone assembly of claim 30 or the headset assembly of claim 39.

41. A transceiver apparatus comprising a transistor having a first terminal thereof connected to a bidirectional transmit/receive port, a second terminal connected to a receive output, and a third terminal connected to a transmit input, wherein said transistor is operable in a first mode to accept receive signals at said first terminal and convey same to said second terminal, and a second mode to accept transmit signals at said third terminal and convey same to said first terminal.

42. A transceiver apparatus as claimed in claim 41, wherein said transistor is a bi-polar transistor having its emitter connected as said first terminal, its collector connected as said second terminal, and its base connected as said third terminal.

43. A transceiver apparatus as claimed in claim 42, wherein said first mode is a common-base mode and said second mode is a common-collector mode.

44. A transceiver apparatuses claimed in claim 43, further comprising a driver connected to said base for supplying said transmit signals thereto, said driver representing a static low impedance signal path when said transistor is operating in said common-base mode.

45. A transceiver apparatus as claimed in claim 41, wherein said bidirectional port comprises a radio frequency antenna, and said receive output comprises a radio frequency transformer.