CA1204236A - Wireless telephone system with intercom signalling and auxiliary station - Google Patents
Wireless telephone system with intercom signalling and auxiliary stationInfo
- Publication number
- CA1204236A CA1204236A CA000443378A CA443378A CA1204236A CA 1204236 A CA1204236 A CA 1204236A CA 000443378 A CA000443378 A CA 000443378A CA 443378 A CA443378 A CA 443378A CA 1204236 A CA1204236 A CA 1204236A
- Authority
- CA
- Canada
- Prior art keywords
- operated
- subscriber
- extension
- telephone system
- telephone
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/72—Mobile telephones; Cordless telephones, i.e. devices for establishing wireless links to base stations without route selection
- H04M1/725—Cordless telephones
- H04M1/72502—Cordless telephones with one base station connected to a single line
Abstract
WIRELESS TELEPHONE SYSTEM WITH
INTERCOM SIGNALLING AND AUXILIARY STATION
ABSTRACT OF THE DISCLOSURE
A wireless extension telephone system in-cluding a base unit connected to a telephone line and a remote extension unit. Both base and extension units each include a radio receiver and a radio transmitter.
Also associated with the base unit is an auxiliary tele-phone and switch operated intercom signalling means, which when manually operated cause a radio signal to the transmitted to the remote unit for signalling pur-poses after which conversation may insue between users of the auxiliary telephone and the remote extension unit.
INTERCOM SIGNALLING AND AUXILIARY STATION
ABSTRACT OF THE DISCLOSURE
A wireless extension telephone system in-cluding a base unit connected to a telephone line and a remote extension unit. Both base and extension units each include a radio receiver and a radio transmitter.
Also associated with the base unit is an auxiliary tele-phone and switch operated intercom signalling means, which when manually operated cause a radio signal to the transmitted to the remote unit for signalling pur-poses after which conversation may insue between users of the auxiliary telephone and the remote extension unit.
Description
` 1204236 WIRELESS TELEPHONE SYSTEM WITH
INTERCOM SIGNALLING AND AUXILIARY STATION
BACKGROUND OF T~IE INVENTION
1. Technical Field The present invention relates to telephone systems and more particularly to a subscriber's exten-sion telephone that includes a wireless link between the telephone instrument and an associated telephone line, allowing a subscriber to relocate the telephone instrument at will, yet still make and receive tele-phone calls in a conventional manner.
INTERCOM SIGNALLING AND AUXILIARY STATION
BACKGROUND OF T~IE INVENTION
1. Technical Field The present invention relates to telephone systems and more particularly to a subscriber's exten-sion telephone that includes a wireless link between the telephone instrument and an associated telephone line, allowing a subscriber to relocate the telephone instrument at will, yet still make and receive tele-phone calls in a conventional manner.
2. Backqround Art Since the invention of the telephone, personal communication between individuals has grown so that the majority of all individuals in the United States and many other countries all have telephone service readily available. Rather than reach a saturation point when each family has been equipped with a single telephone, the growth trend has continued so that at present many individuals or families have not one, but several tele-phones for use in their residences.
The use of second and third telephones as extension units throughout a residence has become in-creasingly widespread. Previously, when only one tele-phone was installed in a home a central location for this instrument was chosen. However, no single location is perfect; and as a result frequently the housewife while performing daily chores is forced to come some distance, particularly in a large home, to the location of the telephone either to make or receive telephone calls. If the subscriber is in the yard, porch or basement, etc., the lack of proximity to a telephone instrument often results in extra steps and possibly missing a telephone call if the subscriber is unable to respond within a reasonably short period of time after the commencement of a ringing signal ~1~ ~
~ -~k lZ04236 announcing the incoming call. In the trend toward so-called outdoor living today, the subscriber is frequently required to go from the garden or patio to the nearest telephone to answer it. In many cases this may be a substantial distance.
Several solutions to this problem have been proposed. Among these are the use of a number of extension telephones placed in convenient locations throughout the residence. The other is the use of a multiplicity of telephone line jacks, all connected to the telephone line, allowing the subscriber to move a plug equipped telephone instrument from one location to another to always be within easy access. Still another, is the use of long extension cords to connect the telephone instrument to its associated terminal thus allowing limited freedom in relocating the tele-phone. Obviously, all of these solutions lack flex-ibility since the location of the extension telephone or the extension jack while useful at times will still on many occasions be inadequate.
The most satisfactory solution to the ex-tension telephone problem lies in the use of a tele-phone extension instrument that requires no wire con-nections between the instrument and the telelphone line. An instrument such as this utilizing radio waves between terminal equipment connected to the telephone line and the instrument itself permits the subscriber to locate the telephone instrument any place within a specififed range of telephone line terminal equipment located in the home or other location thus permitting the subscriber to both receive and make telephone calls at some distance from that terminal. Such a wireless extension telephone could be taken to the garden, patio, basement, upstairs, downstairs, etc., and placed in any room in the house as well as possibly carried with the subscriber while visiting a neighbor, so that lZ~Z36 incoming telephone calls would not be missed and so that they might be rapidly answered without consider-able moving about on the part of the subscribr. The advantages of a wireless telephone instrument for subscribers is readily apparent, particularly in the home.
However, it should be pointed out that this same type of instrument would find considerable use in restaurants and other commercial establishments where a person to whom an incoming call is directed would have the telephone brought to him for answering without the necessity for intervening extension cords or other connections. Obviously, the number of pos-sible uses for wireless extension telephones are limit-ed only by the imagination of the users.
Early attempts to provide wireless extension telephones are disclosed in U.S. Patent No. 2,129,332 to Mastini issued September 6, 1938 and U.S. Patent No. 2,894,121 to R. P. Phillips which issued on July 7, 1959. Both of these patents disclose simple wire-less extension telephones employing vacuum tubes.
In both instances, incoming telephone calls use a transmitter associated with the telephone line to generate a carrier signal which is detected by a remote receiver. Likewise, calls initiated at a remote unit are effected by turning on a transmitter, with the carrier signal being detected by a receiver asssociated with the telephone line. The obvious disadvantage of size and large battery requirement etc. stem from the utilization of vacuum tubes, while reliance on detection of carrier wave signals for supervision, i.e.: "on" and "off" hook signal dialing, etc., is less than satisfactory because of the possible effect of RF in~erference caused from extraneous sourcesO
A substantially improved wireless extension telephone is disclosed in U.S. Patent No. 3,193,623, , ,. ,, ~
12~4~36 issued on July 6, 1965 to R. V. Burns et al. The dis-closed wireless extension telephone consisted of tran-sistorized remote base and extension units with the obvious advantages of miniaturization as well as low battery drain. Additionally, full duplex operation is disclosed. "Off: and "on" hook supervisiion and dialing are accomplished by means of tone generation and detection rather than the use of RF carrier tech-niques taught in many of the prior art patents. In the Burns et al patent a tone of a first audio fre-quency super imposed on the RF carrier provides "of"
and "on" hook control from the remote unit and a second audio tone generated at the remote unit provides dial pulse control. A number of other units employing different techniques such as sequential control, "touch calling" signalling, etc., have been taught in U.S.
Patents No. 3,721,771, 4,039,760 and 4,053,717. All of the above units, however, suffer from one or more defects in the area of reliability, size, battery consumption or security ~ccordingly, it is the object of the present invention to provide a new and improved wireless extension telephone overcoming those short-comings found in many previous wireless extension telephones.
SUMMARY OF THE INVENTION
The present invention consists of two prin-cipal portions: a base station connected to a telephone line and a remote station adapted to be located with the base station when not in use so that the internal batteries contained therein may be recharged. The remote unit, however, is removalbe from the base unit and because of its small size extremely portable and capable of being located any place within the operating range of transmitters and receivers contained in both base and remote units.
12(~4236 The base unit as connected to the telephone line includes a self-compensating network similar to that found in many commercial telephones and particular-ly like that found in a subscriber's unit designated Solitare R II manufactured by GTE Automatic Electric Incorporated. Also connected to the line is a ringing signal detector for determining the presence of in-coming ringing signals over the telephone line.
A receiver operable at the same frequency as the transmitter in the remote unit is included in the base station as is a transmitter operating on a second frequency. This second frequency is the same as the receiver operating frequency at the remote unit.
Because of the use of two separate and distinct fre-quencies for transmit and receive in opposite direc-tions between base and remote units, the advantages of full duplex operation are enjoyed.
A power supply included at the base unit provides the necessary operating potentials to the circuitry included in the base unit as well as pro-viding power for charging the batteries included in the remote unit when the remote unit is not in opera-tion. Also included in the base station are a com-bination security tone oscillator and tone filter circuit utilized when the unit is in the "off" hook condition as a filter for incoming security tone sig-nals and in the "on" hook condition as an oscillator to signal the remote unit by means of a discrete se-curity tone to indicate that the telephone line is ringing and the call should be answered. Connected to the security tone oscillator/ filter circuit is an "on" hook/"off" hook control circuit which in re-sponse to the incoming security tone conditions the telephone to go to the "off" hook condition. An a-ssociated security tone dtector detects the securitytone from the remote unit and prevents unauthorized remote units from seizing the telephone line.
! -5-lZ~423~
The base unit further includes a modulator which is connected between the telephone line and a base unit transmitter for the application of audio signals to the transmitter for re-transmission to the remote unit. A gain control or oscillator keyer is provided as well as an audio amplifier that applies audio signals from the receiver included in the remote unit to the telephone line.
Of particular interest in the present unit is the facility for adding an auxiliary phone and a the base unit whereby the auxiliary phone connected to the remote unit can then contact the remote unit on a local or intercom basis. This feature can also be utili~ed in connection with central office calls forthree way conversations.
Much of the structure of the remote unit is similar to that found in the base unit, i.e., there is included a receiver and transmitter operating on frequencies the same as the transmitter and receiver respectively at the base unit. A combination oscilla-tor/filter for generating and receiving security tone with the filter functioning to detect security tone during a remote unit "off" hook condition and acting as an oscillator for generating security tone when the unit is "on" hook. Connected to the oscillator/
filter is the ringer/oscillator amplifier which when the security tone detected by the receiver and passed through the security tone filter generates a tone signal applying it to the remote unit ear piece as an alternating signal. An amplifier is also connected between the ear piece and the remote unit receiver for amplification of incoming signals detected by the remote unit receiver and transmitted from the base unit. The microphone included in the remote unit is connected to a modulator which in turn applies voice signals to the transmitter for transmission to the base unit.
~, 6--` lZ04236 Also included in the remote unit is a dialing circuit which employs a commercially available pulse dialer activated from a ten button key board unit included in the remote unit. A loopstick of conven-tional design is employed as an antenna for the re-ceiver at the remote unit while the transmitter is coupled to a dipole antenna included in the housing of the remote unit.
At the base unit the receiver is connected to a whip antenna while the base unit transmitter is capacitively coupled through an RF choke coil to the AC line providing power to the base unit.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures 1 and 2 placed together with Figure 1 to the left of Figure 2 comprise a combination sche-matic and block diagram of a base unit for a wireless telephone extension unit in accordance with the present invention.
Figure 3 is a combination; schematic and block diagram of a remote unit for a wireless extension telephone in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The circuitry of the base unit will be de-scribed initially. Referring first to Figure 1, the Tip lead of the telephone line connected at terminal T is extended through intercom switch contact 101A
and wiper 101F, (shown in the "normal" non-operated position), through open relay contacts 162A which are not operated at this time, through bridge circuit 106 and terminal R to the Ring conductor of the telephone line. A bypass circuit 106 inclduing capacitor 102, resistor 103 and diodes 104 and 105 provides spark suppression for contacts 162A. Also connected to line terminal T through capacitor 107 and resistor 108 is bridge circuit 111 whose return is to terminal R of the line.
, .
lZ~4236 Bridge 111 forms a portion of ring detector circuit 110 which also includes light emitting diode (LED) 112 and photo transistor 113 (which combined comprise an optical coupler. Additionally, included in the ring detector are resistors 114, 116, 119 and 121, capacitors 115 and 118, diode 117 and operational amplifier 120.
Associated with the ring detector circuitry is operational amplifier 123 (and associated resistor 122) which acts as a buffer to transmit operate gate 125.
As noted previously, the connection to the telephone line at terminals T and R, the Tip lead is extended throu~h contact lOlA on intercom switch 101.
Terminals TA and RA are connected to the Tip (Aux) being cor.nected to intercom switch wiper lOlF and to one side of contacts 162A. When, intercom switch 101 is operated to the intercom position, the Tip (Aux) lead is extended through switch 101 to the intercom signalling circuit 130 which consists of operational signalling circuit 130 which consists of operational amplifier 131 and resistors 132 through 137 and capacitor 138. The output of the intercom signalling circuit is extended through resistor 136 to the positive input of operational amplifier 120 included in the ring detector circuit 110.
Connected to bridge 106 is a self compensating voice network similar to that in the Solitare R telephone manufactured by GTE Automatic Electric Incorporated.
Included in this network are transformer 141 including windings 141A, 141B, 141C and 141D inclusive, varistors 142, 143 and 147 and zener diode 144, resistors 149, 151 and 152 and 153, capacitors 148 and 146 and microphone amplifier 145. Microphone amplifier 145 is of a special design simulating electrically a carbon microphone to the network while permitting the usage of an electret micro-phone. The circuitry of this amplifier is described in detail in the copending patent application Serial No.
273,700 of Hines, Light and Stobbs filed on June 15, 1981, now U.S. Patent 4,400,588. The self-compensating network 140 receives input Z1:~4236 signals from the 49 MHz receiver 100. This receiver in one practical embodiment of the present invention is a dual conversion super-heterodyne 49 MHz receiver of conventional design and construction.
Output signals from the telephone are ex-tended through the self-compensating network 140 to the 1.7 MHz transmitter 200 shown in Figure 2. This transmitter is of conventional design. In a practical embodiment employing frequency modulation, signals from self-compensating network 140 are actually applied through modulator 290 which includes operational ampl-ifier 291 capacitor 292, and resistors 294 and 295.
Additional input to the modulator which shall be dis-cussed later, is applied through capacitor 293. The output of operational amplifier 295 (i.e.: modulator 290) is applied to a varactor diode included in trans-mitter 200 to provide the necessary freuency modula-tion.
Before signals received by the 49 MHz re-ceiver 100 can be extended to the telephone line via self-compensating network 140 the signals are initially extended through resistor 171 to filter/oscillator 210 shown in Figure 2. Filter/oscillator 210 consists of operational amplifiers 213 and 221, resistors 212 through 219 and 224, 225 and 228 as well as capacitors 211, 222 and 223, and diodes 226 and 227. The first section of filter/oscillator 210 associated with oper-ational amplifier 213 is a "Q-multiplier" with the second operational amplifier 221 acting as the filter proper. The overall gain and band width is set by resistors 218 and 219 and the frequency by resistors 216 and 217. Diodes 226, 227 and resistor 225 are inactive during the filter mode, because capacitor 253 provides an AC bypass to ground via the saturated output of a transistor included in operational ampli-fier 251. Operational amplifier 251, resistor 252 and 253 form a portion of the oscillator/filter control ~~' 250 which operates in response to ring detector 110.
_g_ lZ~4236 When operational amplifier 251 is switched "off" in response to the detection of an incoming ringing signal by a ring detector 110, capacitor 253 and the included AC path to ground is disconnected and feedback paths through resistors 225 and 228 and diodes 226 and 227 come into being and cause the circuitry of oscillator/
filter 210 to go into oscillation. Resistor 228, and diodes 226 and 227, limit the amplitude of the oscilla-tion and insure a constant output level over a range of supply voltage and oscillatory frequency. Diode 229 functions to blind the input to the oscillator/
filter 210 during ringing.
Filter/oscillator 210 is connected to several locations including the "on" hook/"off" hook control circuit 230. This circuit consists of operational amplifiers 232 and 239 as well as resistors 231, 232, 234, 235, 236, 238, 241, 242 and 243. Also included in the "on" hook/"off" hook control circuit 230 is capacitor 237. Operational amplifier 232 functions as a threshold detector to generate the necessary dial pulses only by detecting the presence of high level signals at a dial pulse rate from the output of oscilla-tor/filter 210. The actual control function is per-formed by operational amplifier 239 which effectively causes the telephone to go "off" hook when dial tone is detected. Control of operational amplifier 239 is over resistor 243 from security tone detector 270.
Tone detector 270 is a conventionally de-signed tone decoder utilizing a phase locke loop in-tegrated circuit as manufactured by National Semi-conductor under their piece number LM567C or by othermanufacturers. The security tone detector 270 detects a pre-determined particularly frequency of tone gener-ated by an associated remote unit. For example, this tone might be 5100 Hz for one combination of base and remote unit and 4800 Hz for another combination 12~4Z36 of base and remote unit. It should be obvious to those skilled in the art that numerous frequencies or com-binations of frequencies may be utilized between base and remote units to provide the degree of security required in a par~icular system. The quantity of these frequencies is limited obviously only by the capability i.e.: band width, etc. of the phase lock loop circuitry, and the stability of same as included in the security tone detector.
An output is generated by operational ampli-fier 239 and extended to the base of transistor 161 turning it on, making a path available for power to relay 162. The operation of relay 162 at its associated contact 162A completes the path from the line to the transmission network 140 via bridge 106 and the cir-cuitry of the self-compensating network 140 previously outlined. When the collector of transistor 161 is conductive, an operating siqnal is also extended to gate circuit 125 whose output is connected to the 1.7 MHz transmitter 200 turning it on.
Audio amplifier 280 consisting of operational amplifier 281 and resistors 282 through 286 inclusive and capacitor 287, receives voice signals from the 49 MHz receiver 100 and applies those signals through resistor 285 to the self-compensating network 140 through capacitor 146. Also applied through resistor 283 to operational amplifie} 281 is the output from the security tone oscillator/filter 210 which is applied to the positive input with an equal output, equal amplitude and opposite phase to the negati~e input of operational amplifier 281, providing complete can-cellation of the aduio portion of the security tone signal, thus inhibiting security tone audio components from reaching the telephone line.
Gate control circuit 260 consisting of opera-tional amplifier 261 resistors 262, 264, 265 and cap-acitor 263 operates to inhibit the security tone on the input of the 1.7 MHz transmitter 200 during normal lZ~4Z36 talking mode. Security tone signals of maximum ampli-tude are extended through the modulator 290 to the transmitter 200 during the ringing mode.
The power supply for the wireless extension telephone base unit has not been shown since it is essentially of conventional design providing the ne-cessary potentials where required. As a portion of this circuit, a reference voltage is applied throughout portions of the circuitry of the base unit, these locations being identified at terminals marked ER.
The power supply may also include the necessary facil-ity for charging batteries included in the remote unit if desired.
The remote unit of the wireless extension telephone as shown in the Figure 3 includes a 1.8 MHz receiver 300 and a 49 MHz transmitter 390, operating to receive signals transmitted from the base unit and to transmit signals to the base unit on two separate frequencies thus providing full duplex operation. Both the transmitter and the receiver like those used in the base unit are of the frequency modulation type except the receiver is of the single conversion super-heterodyne unit and the transmitter is crystall con-trolled. Power for the remote unit is provided from a battery which may be of the rechargeable type and as noted above, if of the rechargeable type, may be recharged by connection to the power supply included in the base unit.
Included in the remote unit is dial circuit 350 which in a practical embodiment of the remote unit consists of a push button dial structure of conven-tional design connected to an integrated circuit dial pulse generator. The dial pulse generator is a commer-cially available unit avilable from a number of differ-ent manufacturers which in response to contact closures on the key pad produces appropriate trains of dial pulses for signalling purposes. One unit of this type Z~4236 is manufactured by Mostek Inc. and is commercially available under their piece part MK-5175.
Much of the circuitry contained in the wire-less extension telephones remote unit is similar to that included in the base unit and described previous-ly. For example, the security tone oscillator/filter310 consisting of operational amplifiers 311, 321 and asso-ciated components 31~ through 317 and 322 through 328 is virtually identical in construction and opera-tion to the security oscillator 210 found in the base unit. Likewise, the control circuit utilized for changing the mode of operation of the oscillator/filter 310 from filter to oscillator is control circuit 360 con-sisting of operational amplifier 361 and associated resistor 362 and capacitor 363. Structurally and functionally, this circuit corresponds to control circuit 250 found in the base unit.
The modulator circuit 370 while not struc-turally identical to the modulator in the base unit is functionally similar. The modulator 370 consists of operational amplifier 373 driven by microphone 371 and additionally including capacitor 374 and resistors 372, 375, 376, 377, 378 and 379. The output of modu-lator 370 is applied to 49 MHz transmitter 390 where it is applied across a varactor diode which provides for the necessary frequency modulation of the 49 MHz transmitter.
Connected between dial circuit 350 and the modulator 370 is a transistor 351 which functions as a switch to provide a ground path through the tran-sistor and capacitor 354 and resistor 355 to divert or reduce the amplitude of security ~one signals fed to the 49 MHz transmitter and then sent to the base unit. However, during dialing the shunt that provides the modified or attenuated security tone is removed 5 allowing the amplitude of the resultant pulses of security tone to be substantially greater than pre~
viously.
Connected to the output of the 1.7 MH2 re-ceiver 300, in addition to the oscillator/filter 310, is an ear piece amplifier 380 for amplifying incoming voice signals, consising of operational amplifier 381 resistors 282, 384, 386 as well as capacitor 385 and 387 and diode 383. Connected to the output of the amplifier 380 is a telephone ear piece or receiver of conventional design 389. Also connected to ear piece 389 is the output of ringer oscillator 330.
Ringer oscillator 330 consists of three sections, a comparator stage consisting of operational amplifier 331 and associated components 332 through 339, a switch stag consisting of operational amplifier 340 and com-ponents 341 through 344 and the final oscillator stageconsisting of operational amplifier 345 and associated components 346 and 349. The output of oscillator stage is further amplified by transistor 393 which is util-ized in the emitter follower configuration with the output connected to ear piece 389.
Of major importance also in the remote unit circuitry is hook switch 391 which upon operation provides ground during the "off" hook operation of the wireless unit to the 49 MHz transmitter 390 and to the dial circuit 350 for inhibiting ringing.
Further understanding of the present inven-tion may be had by reference to Figures 1, 2 and 3 in connection with the following description of the placement of a telephone call by a subscriber at the wireless extension telephone remote unit. Initially, the subscriber goes to the operating or "off" hook mode by operating hook switch 391. Operation of hook switch 3~1 extends ground to the remote unit trans-mitter 390 turning it on. This also provides ground for operation of control circuit 360. The activation . ;
~ 12~)4236 of control circuit 360 causes removal of the AC ground previously supplied through operational amplifier 361 and capacitor 363 to oscillator/filter circuit 310.
Removal of this ground causes the filter circuit to go into the oscillation mode generating at the output thereof the appropriate security tone. In a practical embodiment of a wireless extension telephone according to the present invention, a frequency of 5100 Hz was utilized for this tone.
The output of the oscillator stage through resistors 379 and 377 is applied to modulator 370 where the output is taken through resistor 378 and extended to 4g MHz transmitter 390. Since transmitter 390 has already been turned on the security tone generated by oscillator 310 and applied through modulator 370 modulates the 49 MHz carrier frequency at that audio frequency causing the security signal to be radiated from the antenna associated with transmitter 390.
At the base unit, the 49 MHz signal from the remote unit is detected at 49 MHz receiver 100 and the output thereof routed through oscillator/
filter 210 which in the present moment is functioning as a filter circuit. The tone passed through the filter 210 is then extended to security tone detector 270 where if the frequency is the appropriate one (as determined by the internal circuitry included in se-curity tone detector 270), an output is generated and extended through resistor 243 to the negative input of operational amplifier 239 which is a part of the "on" hook/"off" hook control circuit 230 of the base unit. The output from "off" hook/"on" hook control circuit 230 is applied from operational amplifier 239 to the base of transistor 161, turning it on and pro-viding a path to ground for relay 162 causing it to operate, closing at associated contacts 162A a path across the Tip and Ring leads extending to the tele-phone line, causing line seizure. Operation of tran-sistor 161 also through gate 125 turns on transmitter 200.
~15--` 1209~Z36 With connection of the self-compensating network 140 through bridge circuit 106 to the tele-phone line, via terminals T and R and closed contact 162A, the proper conditions are now present for line seizure at the associated telephone central office to which the line is connected. At this point upon line seizure, dial tone will be returned over the line and extended back through the self-compensating network 140 and specifically through resistor 152 to modulator 290 where the dial tone signal is then applied to transmitter 200 which is modulated at the dial tone frequency and then transmitted at a frequency of 1.7 MHz via the associated antenna.
The radiated signal is received at the wire-less extension unit remote unit by 1.7 MHz receiver 300, with the output therefrom applied through resistor 303 and conducted through amplifier 380 to the ear piece 389 where the dial tone is heard by the sub-scriber. The subscriber on hearing dial tone will now operate the key pad (not shown) associated with dial circuit 350 to generate the required dial pulses to signal a desired party. Output pulses from dial circuit 350 are applied to the base of ~ransistor 351 where for each transmitted pulse, ground is removed at the collector which thus removes resistor 355 from its previous function in the modulator 370 circuit.
Thus during each dial pulse this results in a high amplitude signal being extended from the seurity tone oscillator through to the 49 MHz transmitter 390. This higher level dial pulse signal is then of course sent out from the transmitter, received at the base unit receiver 100 and extended through resistor 171 to the oscillator/filter circuit 210 which is still functioning in filter mode. These dial pulse signals from filter circuit 210 are then extended to the "on" hook/"off"
hook control circuit 230 through resistor 231 which acts to turn off integrated circuit 239 at the dial pulse rate. This is accomplished by operational ampli-1204;~36 fier 232 and its associated components which function as a threshold detector, and in response to high level (amplitude) signal, turn integrated circuit 239 of for each received pulse signal. Thus transistor 161 at the base unit also turns off and on at the dial pulse rate causing associated relay 162 to operate off and on opening and closing associated contacts 162A thus opening and closing the line at the dial pulse rate causing the dial pulses to be extended to the telephone central office over the line.
After the dial pulses are extended to the telephone central office, the central office will provide the necessary switching connection in the usual manner and provide connection to the called subscriber.
Upon completing, said connection ring back tone is sent back from the telephone central office over the telephone line to the wireless extension base unit where the tone is applied to the transmitter through the modulator in much the same manner as the previous dial tone was repeated. The ring back tone is then detected at the extension unit, by the receiver 300, amplified by ear piece amplifier 381, in turn repro-duced by ear piece 389. The subscriber at the remote unit now waits until the party at the called station answers after which conversation may ensue, incoming voice signals from the telephone central office being extended to the remote station in the manner previously described. The subscriber at the remote unit speaks into the micro-phone 371 whose output is applied through modulator 370 in the normal manner to the telephone transmitter 390. At the base unit receiver 100 the voice signals are received and coupled from the output thereof through capacitor 172 to the telephone line amplifier 280, whose output is extended via the self-compensating network 140, terminals T and R and the telephone line to the telephone central office. In this manner, normal conversation to a telephone central office takes place.
12~4Z36 At the conclusion of the conversation, the subscriber at the remote station places his unit in the "on" hook or non-operated condition by restoring hookswitch 391, removing ground from the 49 MHz trans-mitter 390 and dialing circuit 350, causing termination of transmitted signals from the transmitter 390. At the base station, the lack of a signal being detected by the 49 MHz receiver 100 removes the security tone through resistor 171 from the input to oscillator/
filter 210 thus removing tone from security tone de-tector 270 causing operational amplifier 239 of "on"
hook/"off" hook control circuit 230 to turn "off" which in turn, turns transistor 161 off, causing relay 162 to restore, opening at its associated contacts 162A, thus effectively disconnecting the station from the telephone line. If the subscriber at the distant endof the telephone call hangs up first, dial tone will be returned from the telephone central office and when this signal is heard by the subscriber at the remote extension unit, he then realizes that he too should go to the "on" hook or non-operative mode after which the sequence described above will take place.
For an additional understanding of the pre-sent invention, the following description will be given and will describe the extension of a call initiated at a distant location through a telephone central office and over the telephone line to the wirelss ex-tension telephone of the present invention. Assuming that the telephone central office has extended the call over the telephone line via terminals T and R
to the wireless extension telephone base unit, incoming ringing signals are extended via the previously de-scribed path to ring detector circuit 110 and speci-fically through bridge circuit 111 and the opitcal coupler consisting of LED 112 and photo transistor 113 where the output is extended to operational ampl-ifier 120 and then to mode control circuit 250 causing `` ~Z~4236 oscillator/filter circuit 210 to go into the oscilla-tory mode. The output of ring detector circuitry 110 is also extended through operational amplifier 123 to transmit control gate 125 which functions to turn on the 1.7 MHz transmitter 200. The output from the oscillator/filter circuit 210 now operating in the oscillatory mode is applied to modulator circuit 290 which modulates transmitter 200 at the security tone frequency generated by oscilla-tor/fiter 210. Trans-mitter 2~0 then transmits 1.7 MHz RF signals modulated at the security tone frequency.
The signal transmitted by the base unit is received at the extension unit 1.7 MHz receiver 300 and then conducted to oscillator/filter circuit 310 which is functioning in the filter mode at the remote unit. It should be noted at this time the remote unit is still in the l'onl' hook or not operated condition.
Output from the filter section taken from operational amplifier 321 is applied to the ringer oscillator 330, through to its associated amplifier transistor 393 to the ear piece 389 where the operation of the ringer oscillator causes the ear piece to emit a distinctive tone to signal the presence of an incoming call to the subscriber at the remote extension unit. On hear-ing the alerting signal, the subscriber operates the hookswitch 391 placing ground on transmitter 390 caus-ing it to operate. The 49 MHz transmitter 390 operates in the previously described manner extending a security tone signal to the base unit where its detected pre-sence activiates all of the circuitry at the base unit in the manner previously described. Conversation can now ensure. Disconnect after the call has been com-pleted also takes place in the manner previously out-lined.
A final mode of operation of the wireless extension telephone in accordance with the present invention, is that of the intercom mode. ~n this moade, it is necessary that an auxiliary telephone be connected at leads TA and RA of the base unit as shown in Figure 1. Assuming that an incoming call 12~4236 has been answered by a subscriber at the auxiliary phone, and it is desired to extend that telephone call from the central office to the wireless extension remote unit, the subscriber at the auxiliary phone operates intercom switch 101, maintaining the switch in the operated mode until the subscriber at the remote unit responds. When the sub-scriber at the auxiliary phone operates intercom switch 101, battery is applied through the switch contact lOlD, and over terminal RA, through the auxiliary phone and terminal TA through contacts lOlB to the input of intercom signalling circuit 130 and specifically via resistor 132 to the positive input of operational amplifier 131. This battery application causes a periodic output from circuit 130 to be generated and extended through re-sistor 136 to ring detector circuit 110 where it is detected in much the same manner as the output from the opitcal coupler previously de scribed. When this intercom signalling is detected, the sequence of oper-ations follows the same path as previously described for an incoming call.
As the name implies the intercom switch 101 can also be operated to establish communication between the auxiliary phone connected to the base unit and the associated wireless remote extension unit. No central office call need be involved. In this mode of operation after the subscriber at the extension unit has answered, the party at the auxiliary phone restores intercom switch to its normal position and communication between the extension unit and the aux-iliary phone can take place inasmuch as both phonesare directly connected. It is also possible to estab-lish a three way conversation between the auxiliary phone, the wireless extension unit, and a caller ac-cessing the present invention over a line from the telephone central office.
While not a single embodiment of the present invention has been shown, it will be obvious to those skilled in the art that numerous modifications may -20~
--`` lZ04236 be made to the disclosed embodiment without departing from the spirit and scope of the invention which shall be limited only by the claims appended thereto.
The use of second and third telephones as extension units throughout a residence has become in-creasingly widespread. Previously, when only one tele-phone was installed in a home a central location for this instrument was chosen. However, no single location is perfect; and as a result frequently the housewife while performing daily chores is forced to come some distance, particularly in a large home, to the location of the telephone either to make or receive telephone calls. If the subscriber is in the yard, porch or basement, etc., the lack of proximity to a telephone instrument often results in extra steps and possibly missing a telephone call if the subscriber is unable to respond within a reasonably short period of time after the commencement of a ringing signal ~1~ ~
~ -~k lZ04236 announcing the incoming call. In the trend toward so-called outdoor living today, the subscriber is frequently required to go from the garden or patio to the nearest telephone to answer it. In many cases this may be a substantial distance.
Several solutions to this problem have been proposed. Among these are the use of a number of extension telephones placed in convenient locations throughout the residence. The other is the use of a multiplicity of telephone line jacks, all connected to the telephone line, allowing the subscriber to move a plug equipped telephone instrument from one location to another to always be within easy access. Still another, is the use of long extension cords to connect the telephone instrument to its associated terminal thus allowing limited freedom in relocating the tele-phone. Obviously, all of these solutions lack flex-ibility since the location of the extension telephone or the extension jack while useful at times will still on many occasions be inadequate.
The most satisfactory solution to the ex-tension telephone problem lies in the use of a tele-phone extension instrument that requires no wire con-nections between the instrument and the telelphone line. An instrument such as this utilizing radio waves between terminal equipment connected to the telephone line and the instrument itself permits the subscriber to locate the telephone instrument any place within a specififed range of telephone line terminal equipment located in the home or other location thus permitting the subscriber to both receive and make telephone calls at some distance from that terminal. Such a wireless extension telephone could be taken to the garden, patio, basement, upstairs, downstairs, etc., and placed in any room in the house as well as possibly carried with the subscriber while visiting a neighbor, so that lZ~Z36 incoming telephone calls would not be missed and so that they might be rapidly answered without consider-able moving about on the part of the subscribr. The advantages of a wireless telephone instrument for subscribers is readily apparent, particularly in the home.
However, it should be pointed out that this same type of instrument would find considerable use in restaurants and other commercial establishments where a person to whom an incoming call is directed would have the telephone brought to him for answering without the necessity for intervening extension cords or other connections. Obviously, the number of pos-sible uses for wireless extension telephones are limit-ed only by the imagination of the users.
Early attempts to provide wireless extension telephones are disclosed in U.S. Patent No. 2,129,332 to Mastini issued September 6, 1938 and U.S. Patent No. 2,894,121 to R. P. Phillips which issued on July 7, 1959. Both of these patents disclose simple wire-less extension telephones employing vacuum tubes.
In both instances, incoming telephone calls use a transmitter associated with the telephone line to generate a carrier signal which is detected by a remote receiver. Likewise, calls initiated at a remote unit are effected by turning on a transmitter, with the carrier signal being detected by a receiver asssociated with the telephone line. The obvious disadvantage of size and large battery requirement etc. stem from the utilization of vacuum tubes, while reliance on detection of carrier wave signals for supervision, i.e.: "on" and "off" hook signal dialing, etc., is less than satisfactory because of the possible effect of RF in~erference caused from extraneous sourcesO
A substantially improved wireless extension telephone is disclosed in U.S. Patent No. 3,193,623, , ,. ,, ~
12~4~36 issued on July 6, 1965 to R. V. Burns et al. The dis-closed wireless extension telephone consisted of tran-sistorized remote base and extension units with the obvious advantages of miniaturization as well as low battery drain. Additionally, full duplex operation is disclosed. "Off: and "on" hook supervisiion and dialing are accomplished by means of tone generation and detection rather than the use of RF carrier tech-niques taught in many of the prior art patents. In the Burns et al patent a tone of a first audio fre-quency super imposed on the RF carrier provides "of"
and "on" hook control from the remote unit and a second audio tone generated at the remote unit provides dial pulse control. A number of other units employing different techniques such as sequential control, "touch calling" signalling, etc., have been taught in U.S.
Patents No. 3,721,771, 4,039,760 and 4,053,717. All of the above units, however, suffer from one or more defects in the area of reliability, size, battery consumption or security ~ccordingly, it is the object of the present invention to provide a new and improved wireless extension telephone overcoming those short-comings found in many previous wireless extension telephones.
SUMMARY OF THE INVENTION
The present invention consists of two prin-cipal portions: a base station connected to a telephone line and a remote station adapted to be located with the base station when not in use so that the internal batteries contained therein may be recharged. The remote unit, however, is removalbe from the base unit and because of its small size extremely portable and capable of being located any place within the operating range of transmitters and receivers contained in both base and remote units.
12(~4236 The base unit as connected to the telephone line includes a self-compensating network similar to that found in many commercial telephones and particular-ly like that found in a subscriber's unit designated Solitare R II manufactured by GTE Automatic Electric Incorporated. Also connected to the line is a ringing signal detector for determining the presence of in-coming ringing signals over the telephone line.
A receiver operable at the same frequency as the transmitter in the remote unit is included in the base station as is a transmitter operating on a second frequency. This second frequency is the same as the receiver operating frequency at the remote unit.
Because of the use of two separate and distinct fre-quencies for transmit and receive in opposite direc-tions between base and remote units, the advantages of full duplex operation are enjoyed.
A power supply included at the base unit provides the necessary operating potentials to the circuitry included in the base unit as well as pro-viding power for charging the batteries included in the remote unit when the remote unit is not in opera-tion. Also included in the base station are a com-bination security tone oscillator and tone filter circuit utilized when the unit is in the "off" hook condition as a filter for incoming security tone sig-nals and in the "on" hook condition as an oscillator to signal the remote unit by means of a discrete se-curity tone to indicate that the telephone line is ringing and the call should be answered. Connected to the security tone oscillator/ filter circuit is an "on" hook/"off" hook control circuit which in re-sponse to the incoming security tone conditions the telephone to go to the "off" hook condition. An a-ssociated security tone dtector detects the securitytone from the remote unit and prevents unauthorized remote units from seizing the telephone line.
! -5-lZ~423~
The base unit further includes a modulator which is connected between the telephone line and a base unit transmitter for the application of audio signals to the transmitter for re-transmission to the remote unit. A gain control or oscillator keyer is provided as well as an audio amplifier that applies audio signals from the receiver included in the remote unit to the telephone line.
Of particular interest in the present unit is the facility for adding an auxiliary phone and a the base unit whereby the auxiliary phone connected to the remote unit can then contact the remote unit on a local or intercom basis. This feature can also be utili~ed in connection with central office calls forthree way conversations.
Much of the structure of the remote unit is similar to that found in the base unit, i.e., there is included a receiver and transmitter operating on frequencies the same as the transmitter and receiver respectively at the base unit. A combination oscilla-tor/filter for generating and receiving security tone with the filter functioning to detect security tone during a remote unit "off" hook condition and acting as an oscillator for generating security tone when the unit is "on" hook. Connected to the oscillator/
filter is the ringer/oscillator amplifier which when the security tone detected by the receiver and passed through the security tone filter generates a tone signal applying it to the remote unit ear piece as an alternating signal. An amplifier is also connected between the ear piece and the remote unit receiver for amplification of incoming signals detected by the remote unit receiver and transmitted from the base unit. The microphone included in the remote unit is connected to a modulator which in turn applies voice signals to the transmitter for transmission to the base unit.
~, 6--` lZ04236 Also included in the remote unit is a dialing circuit which employs a commercially available pulse dialer activated from a ten button key board unit included in the remote unit. A loopstick of conven-tional design is employed as an antenna for the re-ceiver at the remote unit while the transmitter is coupled to a dipole antenna included in the housing of the remote unit.
At the base unit the receiver is connected to a whip antenna while the base unit transmitter is capacitively coupled through an RF choke coil to the AC line providing power to the base unit.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures 1 and 2 placed together with Figure 1 to the left of Figure 2 comprise a combination sche-matic and block diagram of a base unit for a wireless telephone extension unit in accordance with the present invention.
Figure 3 is a combination; schematic and block diagram of a remote unit for a wireless extension telephone in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The circuitry of the base unit will be de-scribed initially. Referring first to Figure 1, the Tip lead of the telephone line connected at terminal T is extended through intercom switch contact 101A
and wiper 101F, (shown in the "normal" non-operated position), through open relay contacts 162A which are not operated at this time, through bridge circuit 106 and terminal R to the Ring conductor of the telephone line. A bypass circuit 106 inclduing capacitor 102, resistor 103 and diodes 104 and 105 provides spark suppression for contacts 162A. Also connected to line terminal T through capacitor 107 and resistor 108 is bridge circuit 111 whose return is to terminal R of the line.
, .
lZ~4236 Bridge 111 forms a portion of ring detector circuit 110 which also includes light emitting diode (LED) 112 and photo transistor 113 (which combined comprise an optical coupler. Additionally, included in the ring detector are resistors 114, 116, 119 and 121, capacitors 115 and 118, diode 117 and operational amplifier 120.
Associated with the ring detector circuitry is operational amplifier 123 (and associated resistor 122) which acts as a buffer to transmit operate gate 125.
As noted previously, the connection to the telephone line at terminals T and R, the Tip lead is extended throu~h contact lOlA on intercom switch 101.
Terminals TA and RA are connected to the Tip (Aux) being cor.nected to intercom switch wiper lOlF and to one side of contacts 162A. When, intercom switch 101 is operated to the intercom position, the Tip (Aux) lead is extended through switch 101 to the intercom signalling circuit 130 which consists of operational signalling circuit 130 which consists of operational amplifier 131 and resistors 132 through 137 and capacitor 138. The output of the intercom signalling circuit is extended through resistor 136 to the positive input of operational amplifier 120 included in the ring detector circuit 110.
Connected to bridge 106 is a self compensating voice network similar to that in the Solitare R telephone manufactured by GTE Automatic Electric Incorporated.
Included in this network are transformer 141 including windings 141A, 141B, 141C and 141D inclusive, varistors 142, 143 and 147 and zener diode 144, resistors 149, 151 and 152 and 153, capacitors 148 and 146 and microphone amplifier 145. Microphone amplifier 145 is of a special design simulating electrically a carbon microphone to the network while permitting the usage of an electret micro-phone. The circuitry of this amplifier is described in detail in the copending patent application Serial No.
273,700 of Hines, Light and Stobbs filed on June 15, 1981, now U.S. Patent 4,400,588. The self-compensating network 140 receives input Z1:~4236 signals from the 49 MHz receiver 100. This receiver in one practical embodiment of the present invention is a dual conversion super-heterodyne 49 MHz receiver of conventional design and construction.
Output signals from the telephone are ex-tended through the self-compensating network 140 to the 1.7 MHz transmitter 200 shown in Figure 2. This transmitter is of conventional design. In a practical embodiment employing frequency modulation, signals from self-compensating network 140 are actually applied through modulator 290 which includes operational ampl-ifier 291 capacitor 292, and resistors 294 and 295.
Additional input to the modulator which shall be dis-cussed later, is applied through capacitor 293. The output of operational amplifier 295 (i.e.: modulator 290) is applied to a varactor diode included in trans-mitter 200 to provide the necessary freuency modula-tion.
Before signals received by the 49 MHz re-ceiver 100 can be extended to the telephone line via self-compensating network 140 the signals are initially extended through resistor 171 to filter/oscillator 210 shown in Figure 2. Filter/oscillator 210 consists of operational amplifiers 213 and 221, resistors 212 through 219 and 224, 225 and 228 as well as capacitors 211, 222 and 223, and diodes 226 and 227. The first section of filter/oscillator 210 associated with oper-ational amplifier 213 is a "Q-multiplier" with the second operational amplifier 221 acting as the filter proper. The overall gain and band width is set by resistors 218 and 219 and the frequency by resistors 216 and 217. Diodes 226, 227 and resistor 225 are inactive during the filter mode, because capacitor 253 provides an AC bypass to ground via the saturated output of a transistor included in operational ampli-fier 251. Operational amplifier 251, resistor 252 and 253 form a portion of the oscillator/filter control ~~' 250 which operates in response to ring detector 110.
_g_ lZ~4236 When operational amplifier 251 is switched "off" in response to the detection of an incoming ringing signal by a ring detector 110, capacitor 253 and the included AC path to ground is disconnected and feedback paths through resistors 225 and 228 and diodes 226 and 227 come into being and cause the circuitry of oscillator/
filter 210 to go into oscillation. Resistor 228, and diodes 226 and 227, limit the amplitude of the oscilla-tion and insure a constant output level over a range of supply voltage and oscillatory frequency. Diode 229 functions to blind the input to the oscillator/
filter 210 during ringing.
Filter/oscillator 210 is connected to several locations including the "on" hook/"off" hook control circuit 230. This circuit consists of operational amplifiers 232 and 239 as well as resistors 231, 232, 234, 235, 236, 238, 241, 242 and 243. Also included in the "on" hook/"off" hook control circuit 230 is capacitor 237. Operational amplifier 232 functions as a threshold detector to generate the necessary dial pulses only by detecting the presence of high level signals at a dial pulse rate from the output of oscilla-tor/filter 210. The actual control function is per-formed by operational amplifier 239 which effectively causes the telephone to go "off" hook when dial tone is detected. Control of operational amplifier 239 is over resistor 243 from security tone detector 270.
Tone detector 270 is a conventionally de-signed tone decoder utilizing a phase locke loop in-tegrated circuit as manufactured by National Semi-conductor under their piece number LM567C or by othermanufacturers. The security tone detector 270 detects a pre-determined particularly frequency of tone gener-ated by an associated remote unit. For example, this tone might be 5100 Hz for one combination of base and remote unit and 4800 Hz for another combination 12~4Z36 of base and remote unit. It should be obvious to those skilled in the art that numerous frequencies or com-binations of frequencies may be utilized between base and remote units to provide the degree of security required in a par~icular system. The quantity of these frequencies is limited obviously only by the capability i.e.: band width, etc. of the phase lock loop circuitry, and the stability of same as included in the security tone detector.
An output is generated by operational ampli-fier 239 and extended to the base of transistor 161 turning it on, making a path available for power to relay 162. The operation of relay 162 at its associated contact 162A completes the path from the line to the transmission network 140 via bridge 106 and the cir-cuitry of the self-compensating network 140 previously outlined. When the collector of transistor 161 is conductive, an operating siqnal is also extended to gate circuit 125 whose output is connected to the 1.7 MHz transmitter 200 turning it on.
Audio amplifier 280 consisting of operational amplifier 281 and resistors 282 through 286 inclusive and capacitor 287, receives voice signals from the 49 MHz receiver 100 and applies those signals through resistor 285 to the self-compensating network 140 through capacitor 146. Also applied through resistor 283 to operational amplifie} 281 is the output from the security tone oscillator/filter 210 which is applied to the positive input with an equal output, equal amplitude and opposite phase to the negati~e input of operational amplifier 281, providing complete can-cellation of the aduio portion of the security tone signal, thus inhibiting security tone audio components from reaching the telephone line.
Gate control circuit 260 consisting of opera-tional amplifier 261 resistors 262, 264, 265 and cap-acitor 263 operates to inhibit the security tone on the input of the 1.7 MHz transmitter 200 during normal lZ~4Z36 talking mode. Security tone signals of maximum ampli-tude are extended through the modulator 290 to the transmitter 200 during the ringing mode.
The power supply for the wireless extension telephone base unit has not been shown since it is essentially of conventional design providing the ne-cessary potentials where required. As a portion of this circuit, a reference voltage is applied throughout portions of the circuitry of the base unit, these locations being identified at terminals marked ER.
The power supply may also include the necessary facil-ity for charging batteries included in the remote unit if desired.
The remote unit of the wireless extension telephone as shown in the Figure 3 includes a 1.8 MHz receiver 300 and a 49 MHz transmitter 390, operating to receive signals transmitted from the base unit and to transmit signals to the base unit on two separate frequencies thus providing full duplex operation. Both the transmitter and the receiver like those used in the base unit are of the frequency modulation type except the receiver is of the single conversion super-heterodyne unit and the transmitter is crystall con-trolled. Power for the remote unit is provided from a battery which may be of the rechargeable type and as noted above, if of the rechargeable type, may be recharged by connection to the power supply included in the base unit.
Included in the remote unit is dial circuit 350 which in a practical embodiment of the remote unit consists of a push button dial structure of conven-tional design connected to an integrated circuit dial pulse generator. The dial pulse generator is a commer-cially available unit avilable from a number of differ-ent manufacturers which in response to contact closures on the key pad produces appropriate trains of dial pulses for signalling purposes. One unit of this type Z~4236 is manufactured by Mostek Inc. and is commercially available under their piece part MK-5175.
Much of the circuitry contained in the wire-less extension telephones remote unit is similar to that included in the base unit and described previous-ly. For example, the security tone oscillator/filter310 consisting of operational amplifiers 311, 321 and asso-ciated components 31~ through 317 and 322 through 328 is virtually identical in construction and opera-tion to the security oscillator 210 found in the base unit. Likewise, the control circuit utilized for changing the mode of operation of the oscillator/filter 310 from filter to oscillator is control circuit 360 con-sisting of operational amplifier 361 and associated resistor 362 and capacitor 363. Structurally and functionally, this circuit corresponds to control circuit 250 found in the base unit.
The modulator circuit 370 while not struc-turally identical to the modulator in the base unit is functionally similar. The modulator 370 consists of operational amplifier 373 driven by microphone 371 and additionally including capacitor 374 and resistors 372, 375, 376, 377, 378 and 379. The output of modu-lator 370 is applied to 49 MHz transmitter 390 where it is applied across a varactor diode which provides for the necessary frequency modulation of the 49 MHz transmitter.
Connected between dial circuit 350 and the modulator 370 is a transistor 351 which functions as a switch to provide a ground path through the tran-sistor and capacitor 354 and resistor 355 to divert or reduce the amplitude of security ~one signals fed to the 49 MHz transmitter and then sent to the base unit. However, during dialing the shunt that provides the modified or attenuated security tone is removed 5 allowing the amplitude of the resultant pulses of security tone to be substantially greater than pre~
viously.
Connected to the output of the 1.7 MH2 re-ceiver 300, in addition to the oscillator/filter 310, is an ear piece amplifier 380 for amplifying incoming voice signals, consising of operational amplifier 381 resistors 282, 384, 386 as well as capacitor 385 and 387 and diode 383. Connected to the output of the amplifier 380 is a telephone ear piece or receiver of conventional design 389. Also connected to ear piece 389 is the output of ringer oscillator 330.
Ringer oscillator 330 consists of three sections, a comparator stage consisting of operational amplifier 331 and associated components 332 through 339, a switch stag consisting of operational amplifier 340 and com-ponents 341 through 344 and the final oscillator stageconsisting of operational amplifier 345 and associated components 346 and 349. The output of oscillator stage is further amplified by transistor 393 which is util-ized in the emitter follower configuration with the output connected to ear piece 389.
Of major importance also in the remote unit circuitry is hook switch 391 which upon operation provides ground during the "off" hook operation of the wireless unit to the 49 MHz transmitter 390 and to the dial circuit 350 for inhibiting ringing.
Further understanding of the present inven-tion may be had by reference to Figures 1, 2 and 3 in connection with the following description of the placement of a telephone call by a subscriber at the wireless extension telephone remote unit. Initially, the subscriber goes to the operating or "off" hook mode by operating hook switch 391. Operation of hook switch 3~1 extends ground to the remote unit trans-mitter 390 turning it on. This also provides ground for operation of control circuit 360. The activation . ;
~ 12~)4236 of control circuit 360 causes removal of the AC ground previously supplied through operational amplifier 361 and capacitor 363 to oscillator/filter circuit 310.
Removal of this ground causes the filter circuit to go into the oscillation mode generating at the output thereof the appropriate security tone. In a practical embodiment of a wireless extension telephone according to the present invention, a frequency of 5100 Hz was utilized for this tone.
The output of the oscillator stage through resistors 379 and 377 is applied to modulator 370 where the output is taken through resistor 378 and extended to 4g MHz transmitter 390. Since transmitter 390 has already been turned on the security tone generated by oscillator 310 and applied through modulator 370 modulates the 49 MHz carrier frequency at that audio frequency causing the security signal to be radiated from the antenna associated with transmitter 390.
At the base unit, the 49 MHz signal from the remote unit is detected at 49 MHz receiver 100 and the output thereof routed through oscillator/
filter 210 which in the present moment is functioning as a filter circuit. The tone passed through the filter 210 is then extended to security tone detector 270 where if the frequency is the appropriate one (as determined by the internal circuitry included in se-curity tone detector 270), an output is generated and extended through resistor 243 to the negative input of operational amplifier 239 which is a part of the "on" hook/"off" hook control circuit 230 of the base unit. The output from "off" hook/"on" hook control circuit 230 is applied from operational amplifier 239 to the base of transistor 161, turning it on and pro-viding a path to ground for relay 162 causing it to operate, closing at associated contacts 162A a path across the Tip and Ring leads extending to the tele-phone line, causing line seizure. Operation of tran-sistor 161 also through gate 125 turns on transmitter 200.
~15--` 1209~Z36 With connection of the self-compensating network 140 through bridge circuit 106 to the tele-phone line, via terminals T and R and closed contact 162A, the proper conditions are now present for line seizure at the associated telephone central office to which the line is connected. At this point upon line seizure, dial tone will be returned over the line and extended back through the self-compensating network 140 and specifically through resistor 152 to modulator 290 where the dial tone signal is then applied to transmitter 200 which is modulated at the dial tone frequency and then transmitted at a frequency of 1.7 MHz via the associated antenna.
The radiated signal is received at the wire-less extension unit remote unit by 1.7 MHz receiver 300, with the output therefrom applied through resistor 303 and conducted through amplifier 380 to the ear piece 389 where the dial tone is heard by the sub-scriber. The subscriber on hearing dial tone will now operate the key pad (not shown) associated with dial circuit 350 to generate the required dial pulses to signal a desired party. Output pulses from dial circuit 350 are applied to the base of ~ransistor 351 where for each transmitted pulse, ground is removed at the collector which thus removes resistor 355 from its previous function in the modulator 370 circuit.
Thus during each dial pulse this results in a high amplitude signal being extended from the seurity tone oscillator through to the 49 MHz transmitter 390. This higher level dial pulse signal is then of course sent out from the transmitter, received at the base unit receiver 100 and extended through resistor 171 to the oscillator/filter circuit 210 which is still functioning in filter mode. These dial pulse signals from filter circuit 210 are then extended to the "on" hook/"off"
hook control circuit 230 through resistor 231 which acts to turn off integrated circuit 239 at the dial pulse rate. This is accomplished by operational ampli-1204;~36 fier 232 and its associated components which function as a threshold detector, and in response to high level (amplitude) signal, turn integrated circuit 239 of for each received pulse signal. Thus transistor 161 at the base unit also turns off and on at the dial pulse rate causing associated relay 162 to operate off and on opening and closing associated contacts 162A thus opening and closing the line at the dial pulse rate causing the dial pulses to be extended to the telephone central office over the line.
After the dial pulses are extended to the telephone central office, the central office will provide the necessary switching connection in the usual manner and provide connection to the called subscriber.
Upon completing, said connection ring back tone is sent back from the telephone central office over the telephone line to the wireless extension base unit where the tone is applied to the transmitter through the modulator in much the same manner as the previous dial tone was repeated. The ring back tone is then detected at the extension unit, by the receiver 300, amplified by ear piece amplifier 381, in turn repro-duced by ear piece 389. The subscriber at the remote unit now waits until the party at the called station answers after which conversation may ensue, incoming voice signals from the telephone central office being extended to the remote station in the manner previously described. The subscriber at the remote unit speaks into the micro-phone 371 whose output is applied through modulator 370 in the normal manner to the telephone transmitter 390. At the base unit receiver 100 the voice signals are received and coupled from the output thereof through capacitor 172 to the telephone line amplifier 280, whose output is extended via the self-compensating network 140, terminals T and R and the telephone line to the telephone central office. In this manner, normal conversation to a telephone central office takes place.
12~4Z36 At the conclusion of the conversation, the subscriber at the remote station places his unit in the "on" hook or non-operated condition by restoring hookswitch 391, removing ground from the 49 MHz trans-mitter 390 and dialing circuit 350, causing termination of transmitted signals from the transmitter 390. At the base station, the lack of a signal being detected by the 49 MHz receiver 100 removes the security tone through resistor 171 from the input to oscillator/
filter 210 thus removing tone from security tone de-tector 270 causing operational amplifier 239 of "on"
hook/"off" hook control circuit 230 to turn "off" which in turn, turns transistor 161 off, causing relay 162 to restore, opening at its associated contacts 162A, thus effectively disconnecting the station from the telephone line. If the subscriber at the distant endof the telephone call hangs up first, dial tone will be returned from the telephone central office and when this signal is heard by the subscriber at the remote extension unit, he then realizes that he too should go to the "on" hook or non-operative mode after which the sequence described above will take place.
For an additional understanding of the pre-sent invention, the following description will be given and will describe the extension of a call initiated at a distant location through a telephone central office and over the telephone line to the wirelss ex-tension telephone of the present invention. Assuming that the telephone central office has extended the call over the telephone line via terminals T and R
to the wireless extension telephone base unit, incoming ringing signals are extended via the previously de-scribed path to ring detector circuit 110 and speci-fically through bridge circuit 111 and the opitcal coupler consisting of LED 112 and photo transistor 113 where the output is extended to operational ampl-ifier 120 and then to mode control circuit 250 causing `` ~Z~4236 oscillator/filter circuit 210 to go into the oscilla-tory mode. The output of ring detector circuitry 110 is also extended through operational amplifier 123 to transmit control gate 125 which functions to turn on the 1.7 MHz transmitter 200. The output from the oscillator/filter circuit 210 now operating in the oscillatory mode is applied to modulator circuit 290 which modulates transmitter 200 at the security tone frequency generated by oscilla-tor/fiter 210. Trans-mitter 2~0 then transmits 1.7 MHz RF signals modulated at the security tone frequency.
The signal transmitted by the base unit is received at the extension unit 1.7 MHz receiver 300 and then conducted to oscillator/filter circuit 310 which is functioning in the filter mode at the remote unit. It should be noted at this time the remote unit is still in the l'onl' hook or not operated condition.
Output from the filter section taken from operational amplifier 321 is applied to the ringer oscillator 330, through to its associated amplifier transistor 393 to the ear piece 389 where the operation of the ringer oscillator causes the ear piece to emit a distinctive tone to signal the presence of an incoming call to the subscriber at the remote extension unit. On hear-ing the alerting signal, the subscriber operates the hookswitch 391 placing ground on transmitter 390 caus-ing it to operate. The 49 MHz transmitter 390 operates in the previously described manner extending a security tone signal to the base unit where its detected pre-sence activiates all of the circuitry at the base unit in the manner previously described. Conversation can now ensure. Disconnect after the call has been com-pleted also takes place in the manner previously out-lined.
A final mode of operation of the wireless extension telephone in accordance with the present invention, is that of the intercom mode. ~n this moade, it is necessary that an auxiliary telephone be connected at leads TA and RA of the base unit as shown in Figure 1. Assuming that an incoming call 12~4236 has been answered by a subscriber at the auxiliary phone, and it is desired to extend that telephone call from the central office to the wireless extension remote unit, the subscriber at the auxiliary phone operates intercom switch 101, maintaining the switch in the operated mode until the subscriber at the remote unit responds. When the sub-scriber at the auxiliary phone operates intercom switch 101, battery is applied through the switch contact lOlD, and over terminal RA, through the auxiliary phone and terminal TA through contacts lOlB to the input of intercom signalling circuit 130 and specifically via resistor 132 to the positive input of operational amplifier 131. This battery application causes a periodic output from circuit 130 to be generated and extended through re-sistor 136 to ring detector circuit 110 where it is detected in much the same manner as the output from the opitcal coupler previously de scribed. When this intercom signalling is detected, the sequence of oper-ations follows the same path as previously described for an incoming call.
As the name implies the intercom switch 101 can also be operated to establish communication between the auxiliary phone connected to the base unit and the associated wireless remote extension unit. No central office call need be involved. In this mode of operation after the subscriber at the extension unit has answered, the party at the auxiliary phone restores intercom switch to its normal position and communication between the extension unit and the aux-iliary phone can take place inasmuch as both phonesare directly connected. It is also possible to estab-lish a three way conversation between the auxiliary phone, the wireless extension unit, and a caller ac-cessing the present invention over a line from the telephone central office.
While not a single embodiment of the present invention has been shown, it will be obvious to those skilled in the art that numerous modifications may -20~
--`` lZ04236 be made to the disclosed embodiment without departing from the spirit and scope of the invention which shall be limited only by the claims appended thereto.
Claims (10)
1. A wireless extension telephone system comprising: an extension unit including a radio receiver and a signal transducer connected to said receiver; a base unit including a signalling circuit and switching means connected to said signalling circuit, manually operated to render said signalling circuit operated, signal generating means, ringing detection means, connected between said signalling circuit and said signal generating operated in response to said operated signalling circuit to render said signal generating means operated, a radio transmitter connected to said signal generating means operated in response to said signal generating means to transmit said generated signals; and said receiver at said extension unit operated in response to receipt of said signals transmitted from said base unit transmitter to extend said signals to said signal transducer.
2. A subscriber's extension telephone system as claimed in Claim 1 wherein: the said base unit further includes connections to a telephone line, and said switch-ing means is normally connected to said telephone line thereby connecting base unit to telephone line.
3. A subscriber's extension telephone system as claimed in Claim 2 wherein: there is further included an auxiliary telephone normally connected by said non-operated switching means to said telephone line.
4. A subscriber's extension telephone system as claimed in Claim 1 wherein: there is further included a source of operating potential, connected to said signalling circuit by said operated switching means.
5. A subscriber's extension telephone system as claimed in Claim 1 wherein: said ring detection means in-clude an optical coupler circuit.
6. A subscriber's extension telephone system as claimed in Claim 1 wherein: said extension unit further includes amplifier means connected between said radio re-ceiver and said signal transducer operated to amplify signals received by said receiver and couple said ampli-fied signals to said signal transducer.
7. A subscriber's extension telephone system as claimed in Claim 1 wherein: said signalling means are operated in response to said manual operation to generate a periodic output.
8. A subscriber's extension telephone system as claimed in Claim 7 wherein: said signal generating means comprise a tuned circuit initially operated as a filter and further operated as an oscillator.
9. A subscriber's extension telephone system as claimed in Claim 8 wherein: said base unit further in-cludes a mode control circuit connected to said ring detection means operated to switch said signal generating means from said filter operation to said oscillator operation.
10. A subscriber's extension telephone system as claimed in Claim 9 wherein: said base unit further includes modulator means connected between said signal generating means and said radio transmitter, operated in response to signals from said signal generating means to modulate said transmitter in accordance with said generated signals.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/450,406 US4468539A (en) | 1982-12-16 | 1982-12-16 | Wireless telephone system with intercom signalling and auxiliary station |
| US450,406 | 1982-12-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1204236A true CA1204236A (en) | 1986-05-06 |
Family
ID=23787951
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000443378A Expired CA1204236A (en) | 1982-12-16 | 1983-12-15 | Wireless telephone system with intercom signalling and auxiliary station |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4468539A (en) |
| AU (1) | AU2238983A (en) |
| CA (1) | CA1204236A (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4640987A (en) * | 1984-04-23 | 1987-02-03 | Keizo Tsukada | Cordless telephone |
| JPS60242738A (en) * | 1984-05-17 | 1985-12-02 | Sony Corp | Cordless telephone set |
| JPS60256236A (en) * | 1984-06-01 | 1985-12-17 | Hashimoto Corp | Cordless phone having absence response recording function |
| JPS6373749A (en) | 1986-09-17 | 1988-04-04 | Nec Corp | Switching system between cordless telephone set and wire telephone set |
| JP2888517B2 (en) * | 1987-07-10 | 1999-05-10 | 株式会社東芝 | Cordless telephone equipment |
| FR2620887B1 (en) * | 1987-09-18 | 1990-01-19 | Applic Electro Tech Avance | RADIO-LINKED TELEPHONE INSTALLATION |
| US5010565A (en) * | 1990-06-29 | 1991-04-23 | Bryan Nash | Apparatus and method for adding cordless handset capability to an existing corded telephone |
| DE4026180A1 (en) * | 1990-08-18 | 1992-02-20 | Hannelore Scharn | Telephone installation for main line or PBX working - has console with cradles for cordless and cord-connected handsets |
| FR2691865B1 (en) * | 1992-05-27 | 2001-11-16 | Jacques Lewiner | Improvements to telephone installations including two handsets, one of which is cordless. |
| US5381460A (en) * | 1993-12-30 | 1995-01-10 | Uniden America Corp., | Monitor mode in a portable telephone |
| US20060279405A1 (en) * | 2005-05-17 | 2006-12-14 | Erickson Randall T | Wireless system for alerting hearing-impaired person |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4039760A (en) * | 1974-03-11 | 1977-08-02 | Teletronics United Inc. | Cordless telephone system |
| US3896379A (en) * | 1974-06-10 | 1975-07-22 | Gen Electric | Intercom circuit for a radio transmitter and receiver |
| US4213009A (en) * | 1978-11-03 | 1980-07-15 | Whyte & Hirschboeck S. C. | System of connecting a wire telecommunication and a radio communication |
-
1982
- 1982-12-16 US US06/450,406 patent/US4468539A/en not_active Expired - Fee Related
-
1983
- 1983-12-14 AU AU22389/83A patent/AU2238983A/en not_active Abandoned
- 1983-12-15 CA CA000443378A patent/CA1204236A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4468539A (en) | 1984-08-28 |
| AU2238983A (en) | 1984-06-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |