CA1229134A

CA1229134A - Signal transmitting and/or receiving apparatus

Info

Publication number: CA1229134A
Application number: CA000483280A
Authority: CA
Inventors: Norio Numata
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1984-06-07
Filing date: 1985-06-06
Publication date: 1987-11-10
Also published as: GB2161674B; DE3520441A1; FR2565757A1; DE3520441C2; GB8514172D0; GB2161674A; JPS60260239A; IT8521065A0; KR860000756A; JPH0531859B2; FR2565757B1; IT1184588B; US4650928A

Abstract

ABSTRACT OF THE DISCLOSURE
A cordless telephone comprises a base unit and a plurality of remote units. The remote units are respective-ly adapted to establish radio communication at separate times with the base unit. Each remote unit generates a particular code in a particular format that includes at least one interval in which the particular code is present and at least one interval from which the particular code is absent. The particular code and particular format of each remote unit are different from those of the other remote units. A transmitter in each remote unit transmits the particular code of that unit in the particular format thereof to the base unit. The particular formats are such that the transmission of each particular code periodically corresponds to non-transmission of all of the other particu-lar codes of the remote units. The particular codes can thus periodically be received by the base unit without interference caused by transmission of the other particular codes. The base unit echoes the particular code transmitted by a selected one of the remote units, and each of the remote units detects whether or not its own particular code matches the particular code echoed by the base unit. In response to such a match, a communication channel is estab-lished between the base unit and the one of the remote units in which the match occurs. The communication channel while established precludes establishment of a communication channel between the base unit and any of the other remote units.

Description

' ~2~313~ S02~93 PATENT
BACKGROUND OF THE IEVE~TION

Field of the Invention This invention relates to signal transmitting and reproducing apparatus and, more particularly, to novel and highly-effective signal transmi~ting/reproducing apparatus of a type suitable for use as a cordless telephone and the-.
like.

:
Descrip~on of the Prior Art The cord of a conventional telephone is connected to a base unit that in turn is attached rigidly or by another cord) to a post, wall or the like, so that the range of the movement permitted a user of the telephone is limited by the length of the telephone cord, for example several meters. If the telephone cord is longer than a few meters, so as to extend the range of movement permitted the user, the cord it likely to become tangled, to catch on various Jo objects, to pull small objects from tables, to trip or inconvenience other person in the vicinity, etch To overcome these problems, so-called cordless telephones are becoming more frequently used in the United States and other countries.
A problem with conventional cordless telephones arise when a jingle base unit us used in combination with two or more handsets. In such case, single down charnel common to hot handsets us used for transmi~slon prom the bate unit to the handsets and jingle up channel common to Roth handset is used for transmission from the handsets to the bate unit.

-2-~91~ S02093 PATENT
Accordingly, when the base unit calls the handsets in response to an incoming call, a telephone buzzer or similar device in each of the handsets generates an audible signal. When users of both handsets answer the call of the base unit, both handsets begin transmitting through the same up channel, which results in radio interference. In the worst case, the base unit becomes unable to receive the I-signal from either handset and hence no response can be made to thy incoming call.
Similarly, if the handsets are used by chance in an attempt to make two outgoing calls at substantially the same time, radio interference and a service interruption result.

OBJECTS AND SUMMARY OF THE INVENTION
I, An object of the invention is to provide a signal transmitting and/or receiving apparatus in which, when a base unit is used with a plurality of remote units, a plurality of such remote units can be jet in the talk mode simultaneously without radio interference and a selected one of them can be connected to an outside line correctly.
Another object of the invention is to province a signal transmitting and/or receiving apparatus which can be embodied as a cordless telephone, a transceiver, a carrier 8y8tem inter phone, etc.
According to owe aspect of the present invention, apparatus it provided comparing a base unit and a plurality of remote units, the remote units being respectively adapted to establish radio communication at separate tome with the base unit; each of the remote units oomprlsing: means or 2~9~34 PATENT
generating a particular code in a particular format that include at least one interval in which the particular code us present and at least one interval from which the portico-far code it absent, the particular code end particular format of each remote unit being different from those of the other remote units of the plurality of remote units, and means for transmitting the particular code in the particular format to the base unit; the particular format being such that the transmission of each of the particular odes periodically corresponds Jo non-transmission of all of the other particular codes of the plurality of remote units, whereby each of the particular codes can be periodically received by the base unit without interference caused by transmission of the other particular codes of the plurality of remote units; the base unit comprising means for echoing the particular code transmitted by a selected one of the remote units; and each of the remote units further comprising means for detecting whether or not its own particular code matches the particular code echoed by the base unit; and further comprising means responsive to such a match for establishing a communication channel between the base unit and the one of the plurality of remote units in which such match occur, the communication channel while established precluding establishment of a communication channel between the base unit and any other of the plurality of revote Nat.

BRIEF DESCRIPTION OF THE DRAWINGS
A better understanding of the object, features and advantage of the present invention can be gained from a consideration of the following detailed descr~ptlon of the 1229~39L PATENT
preferred embodiment thereof, taken in conjunction with the accompanying drawings, wherein like reference characters designate like elements and parts, and wherein Fig. 1 is a perspective view of a representative cordless telephone System in accordance wit h the prior art ; and comprising a base unit and a handset;
fig. 2 is a perspective view of a representative.
cordless telephone system in accordance with the prior art and comprising a base unit and two handsets and to which the present invention is applicable;
:- Fig. 3 is a schematic block diagram of a portion of the circuitry of the handset of the present invention;
Fig. 4 is a schematic block diagram of a portion of the circuitry of the base unit of the present invention;
Fig. 5 is a schematic diagram of a lit code signal used in the present invention;
Figs. PA to 6C to Figs. lo to lo are respective-: lye diagrams useful for explaining the present invention;
: - Figs. lea and lob are flow charts showing the operation of the control circuit of the handsets and the base unit, respectively, in response to an incoming call, and Figs. AYE and 12B are flow chart showing the operation of the handsets and the base unit, respectively, in response to an outgoing call.

: DESCRIPTION OF THE PREFERRED EMBODIMENT
_ _ .
; Typically, as Fig. 1 shows, conventional cord-less telephone comprises a transmitter-receiver on the form of a cordless handset 1 and a transmitter-receiver in the , . , " ,, .. , . . , . ... ...... , ......... Jo .. ..

Z29~3~ 502093 PATENT
form of a base unit 2. The base unit 2 is connected to a telephone network line 3. The handset l and the base unit 2 are coupled with each other through radix frequency electromagnetic waves (radio Waves) and a telephone tub-scriber uses the handset 1 in substantially the tame way as he or she would use a standard telephone. Elowever, in using a cordless telephone, the telephone subscriber can move about freely with the handset 1 without fear of jangling a lengthy cord, to The maximum useful distance between the handset 1 and the base unit 2 is referred to as the service radius and is typically about 300 meters. The frequency of the radio waves transmitted between the handset 1 and the base unit 2 it typically in, for example, the 49 My band for the up channel (i.e., for transmission from the handset 1 to the base unit 2) and the 46 MHz band for the down channel it for transmission from the base unit 2 to the handset I In most caves ten duplex channels for each system are permitted by regulations of the FCC the Federal Communications Commission). The above-described values are of course arbitrary and from a technical standpoint can easily be varied.
A single base unit 2 is frequently combined with two handset lo and lo, as Fig. 2 owe In such case, a single down channel (having a carrier frequency id) common to both handsets lo and lo is used for transmission from the base unit to the handset, and a angle up channel shaving a carrier frequency fur common to the both handout lo end lo is used for transmission from the handset to the base unit.

~L229~3~L swig PATENT
Accordingly, when the base unit 2 calls the handsets lo and lo in response to an oncoming call, a telephone buzzer or similar device in each of the handsets lo and lo generates an audible signal. when users of both handsets lo and lo answer the call of the base unit 2, both handsets lo end lo begin transmitting Roy the tame up channel thawing the tarrier frequency fur), which results it radio interference In the worst case, the base unit 2 becomes unable to receive the signal from ether handset and hence no response can be made to the incoming call.
Similarly, if the handsets lo and lo are used by chance in an attempt to make two outgoing calls at sub Stan-.
tidally the same time, radio interference and a ~erviceinterruption result.
In accordance with the invention, a code signal CODE having for example the format shown in Fig. 5 is formed. The code signal CODE is transmitted between the base unit 2 and the handsets lay lo and between the handsets lay lo and the base unit 2 in respective formats as shown for example in Figs. PA to 6C.
A Fig. 5 shows, the rode signal CODE comprises a multiplicity of unit each one word (16 bit) in length Each word of the rode signal CODE is formed of an identify-lung portion ID of B bit, a particular code portion HAND of 2 bits and a control portion DATA of 6 bits. the identify-in portion ID it used to discriminate the combination of handsets lay lo and the be e unit 2 from other ~omblna ions what it, the identifying rode portion ID is selected to be common to one combination of the handsets lay lo and the base unit 2, end to be a different prom all other such PATENT
combinations. the particular code portion HAND I used to discriminate or select the handsets lo and lo in accordance with the ~ollowlng table:
~00~: cod common to the handsets lo and lo ~01~ code pertaining Jo the handset lo loo code per awning to the handset lo The control portion DATA it used as a control signal to ..
control transmission between the handsets lay lo and the base unit 2 When forming a communication channel between the handset lo or lo end the base unit 2, the code signals CODE
are transmitted there between and received.
The code signal CODE is transmitted from the base unit 2 repeatedly and continuously at intervals of one word, as Fig PA shows. ho code signal CODE is transmitted from the handset lo continuous lye three times it during a periodical in length to three words), and the transmission is then interrupted for a period equal in length to two words. This cycle of operation it repeated (Fig. 6B). The code signal CODE is transmitted from the handset lB~twice continuously (i.e., during a period equal in length to two word), and the transmission it then interrupted for a period equal on length to two word. This cycle of operation 18 likewise repeated (Fig. 6C).
When the byway unit 2 receives the rode signal CODE
from the handset lo (in the form shown in Fig. 6B) or lo (in the form shown in Fig. 6C), the base unit 2 tran~m$t~
(echoes) the particular code portion HAND count inked in the received cod signal CODE to both handsets lo Ed lo. When the particular rode portion RAND thus transmitted or echoed . ,, , . ., , . , ., . .. . ., . ,, .. .. , . . . ,, . ., . ... ......... ... .. .. , ., . , . .. . ., . , . .. .. . ......
... , , . . . .. ., . . ..... ..... .... .. . .

PATENT
by the base unit 2 is not the tame as its own particular code portion HAND, the handset lo or lo stops transmitting the code signal CODE; on the other hand, when the particular code portion HARD thus transmitted or echoed by the vase unit 2 is the same as its own particular code portion HAND, the handset lo or lo continues the transmission to establish the communication channel. ., In the following description, in cases where it it not necessary to distinguish between the handsets lo and lo, the handset is identified simply as the handset 1 or convenience. The handset 1 and the base unit 2 communicate with each other through a channel A or a channel B.
Fig. 3 illustrates an example of the circuitry of the handset 1, which comprises a transmitting circuit 110 and a receiving circuit 120. Fig. 4 illustrates an example of the circuitry of the bate unit 2, which comprises a transmitting circuit 210 and a receiving circuit 220.
When an outgoing call is made, an audio signal Sty ;: from a transmitter unit 111 in the handset 1 (Fig. I is .
supplied through an audio frequency amplifier 112 to a frequency modulator 113 which frequency-modulates the audio signal Sty to an YE (frequency-modulated) signal Sup of the up channel A or B. (The electron of the channel A or B is made by a switch 154, as indicated Boyle The FM signal Sup I supplied through a high frequency power amplifier 114 and a bawd past filter 11~ with a pass band that pastes both up channels A and B to an antenna 100 which transmit the FM
signal Sup to the base unit 2.

go ., , ,, . , , , ., . ,, . , .. , . , , ,, , . . , . , . " . ,, , .. , .. " . . ... .. . .... , .. , . . ., . . , . , . .. .. . .

~29~3~ S02093 PATENT
In the base unit 2, the signal (radio wave) Sup from the handset 1 is received by an antenna 200 (Fig. 4).
The received signal Sup is supplied through a band-pa~s filter 221 with a pass band that pastes both up channels and through a high frequency amplifier 222 to a mixer circuit 223. The mixer circuit is supplied alto with an oscillating signal of a predetermined frequency from a local oscillating circuit 224. The signal Sup is thus converted to an interim-dilate frequency signal. the intermediate frequency signal is supplied through an intermediate frequency amplifier 225 to a frequency demodulating circuit 226 which demodulates the intermediate frequency input thereto and produces the audio signal St. The signal Sty is delivered through a signal transmission line comprising an audio frequency amplifier 227, a hybrid circuit 231 and relay means 232 to the telephone network line 3.
The relay means 232 includes an ON/OFF relay circuit for carrying out the ON and OFF functions between the base unit 2 and the telephone network line 3, a hold relay circuit, etch Into shown). The hold relay circuit is used when the base unit 2 and the telephone network line 3 are connected with each other and then the telephone convert swish it temporarily interrupted. In such a case, the hold relay circuit maintain the connection between the bass unit 2 and the telephone network line 3.
Upon receiving an incoming call, n audio signal So (Figs. 3 and 4) from the telephone network fine 3 (Fig.
4) it supplied to a receiver or speaker 128 (Fig. 3) of the handset 1. o'er particularly, the audio signal So from the telephone network fine 3 supplied through the inlay . , , , . . .. .. ..... .. _ .

9~3~ S02~)93 PATENT
transmission line of the relay circuit 232, the hybrid circuit 231 end an audio frequency amplifier 212 to a frequency modulating circuit 213 which modulates the audio anal So to an FM frequency modulated signal So. The signal So it supplied through a high frequency power amply-lien 214 and through a band-pass filter 215 to the Antenna 200, which then transmits the I signal Ed Jo the handset 1 In the handset 1 (Fig. 3), the signal So from the base unit 2 is received by the antenna 100. The received signal So is supplied through a band-pass filter 121 and through a high frequency amplifier 122 to a mixer circuit 123. The mixer circuit 123 is supplied also with an oscillating signal having a predetermined frequency from a local oscillating circuit 124. The signal So is thus converted to an intermediate frequency signal. The interim-dilate frequency signal is supplied through an intermediate frequency amplifier 125 to a frequency demodulating circuit 126 which demodulates the intermediate frequency input thereto and produces the audio signal So. The audio signal So us supplied through an audio frequency amplifier 127 to the receiver or speaker 128.
A control circuit 140 fig. 3) may comprise or example a one-chip microcomputer MSM-6404 manufactured by Ok Electric Industry Co., Ltd., of Japan. The circuit 140 includes a 4-bit CPU central processing unit) 141 for parallel processing, a ROM (read only memory) 142 in which a control program it stored, a RAM random access memory 143 for the work area and an I/O port 144.

ZZ~3~ PATENT
The microcomputer 140 it connected with a keyboard 151, a talk witch 152, a channel switch 154 and dip switch en 155 and 156. The keyboard 151 comprises non-lock push switches for input of the telephone number of a third person to be called. This number it supplied Jo the control circuit 140. The talk witch 152 it a changeover witch having three fixed contacts O, S and T for selection of the operation mode of the handset 1. When the movable contact of the talk witch 152 is connecter to the contact O, the power supply to all of the circuits except the microcomputer 140 is turned off loff-mode). When the movable contact of the talk switch 152 is connected to the contact S, the handset 1 is placed in the mode (standby mode) to receive the signal So from the base unit 2. When the movable contact of the task switch 152 it connected to the contact T, the handset 1 is placed on the mode (talk mode) for voice communication with the base unit 2. The movable contact of the talk switch I52 is normally connected with I: :
the standby contact S.
The channel witch 154 it the changeover switch that changes the communication channel between the handset 1 and the base unit 2 to either channel A or B. The witch 155 is adapted to supply the identifying code ID (Fog. 5) to the microcomputer 1~0. The switch 156 it adapted to supply the particular code HAND (Fig. 5) to the microcomputer 1~0.
In the handset lay I By produced from the swept 156 as the rode RAND fig. 7C), while in the handset lo, produced from the wish 156 BY the code END (Fog. ED).
The output from these keys and switches 151 to 156 are all supplied to the microcomputer 140, indicated above.

I S020~3 PATENT
An ASK (minimum shift keying) modulating circuit 161 is adapted to convert the code signal CODE supplied from the microcomputer 140 in the form of a binary signal to an ASK signal Sum in an audio frequency band. queue ASK signal Sum from the MUSK modulating circuit 161 is supplied to thy amplifier 112.
A reception detecting circuit 162 to connected to the demodulating circuit 126 and detects whether or not the signal So exists by utilizing the fact that the frequency component of the output from the demodulating circuit 125 becomes different in accordance with the presence or absence of the signal So. Its detected signal RET is supplied to - the microcomputer 140.
--- An MAR demodulating circuit 163 is connected to the demodulating circuit 126 and demodulates the original code signal CODE from the MUSK signal Sum sent from the base unit 2. The demodulated code signal CODE is supplied to the microcomputer 140:.
: A cull tone forming circuit 164 us controlled by the microcomputer 140 eon as to from a bell sound signal wring tone signal) when an incoming call is received. The bell found signal is supplied to the amplifier 127.
An hued (light emptying diode) 166 connected to the my rocomputer 140 serves as a busy lamp. When a user attempts to use one of the handsets lo or lo to make an outgoing call end the communication channel has already been : occupied by the other handset lo or lay the TED 166 blinks.
The microcomputer 140 supplies a channel designate in signal OH to the modulating circuit 113 end the local o c~llatLng circuit 124 end alto supplies control goal ~229~3~ S02093 PATENT
OX to the modulator circuit 113, by which the modulating circuit 113 it controlled to deliver or not to deliver the I signal Sup therefrom. Also, the microcomputer 140 up-plies a outing signal MUTE to the amplifier 127~
As Fig. 4 shows, the base unit 2 include a control circuit 240. The control circuit 240 is similar in structure and function to the control circuit 140 of the handset 1. the circuit elements of thy control circuit 240 corresponding to the circuit 141 to 144 of the control circuit 140 are represented with corresponding reference numbers, but in he 200s instead of the loos Since these circuit elements have been explained above, no further explanation thereof is required.
Switches 254 and 255 and circuits 261 to 264 in the base unit 2 are respectively similar to the witches 154 and 155 and the circuits 161 to 164 of the handset 1, and the relevant signals thereof are also similar; thus they require no further explant ion. Particularly, the call tone circuit 264 is adapted to form a tone encode signal TO which corresponds to the telephone number of a third person to be called.
An audible or calling signal detecting circuit 255 is provided which is connected to the telephone network line

3 and detects the audible ringing signal of the incoming Hall. Its Output signal BY is supplied to the microcomputer 240. Between the relay circuit 232 and the microcomputer 240, there provided two-way control signal line aye.
hen an incoming call is made by a third person, the microcomputer 140 and 240 carry out the following operation on accordance with the control programs stored in the Rows 142 and 242.

I PATENT
When an incoming call from a third person it made at an arbitrary time if (Figs. PA through ED), the bell wound signal BY it produced by the detecting circuit 265 (Fig 4) and fiupplied to the microcomputer 240 so that the modulating circuit 213 it enabled by the goal TX to generate the FM signal So, and the code signal CODE is formed by the microcomputer 240. The code signal CODE is -supplied to the modulating circuit 261. The circuit 261 generates the signal Sum which is transmitted through the amplifier 212 on the signal So.
The identifying code ID contained in the transmit-ted code signal CODE is produced by the switch 255, the particular code RAND us represented as ~00~ in order to specify both the handsets lo and lo, and the data code DATA
is the code indicative of the presence of the incoming call.
As Fig. PA shows, the signal CODE is continuously transmit-ted at every oared interval repeatedly from the time if.
In Figs. PA to ED (and elsewhere in the drawings), ~00~, ~01~ and ~10~ in the code signal CODE represent the respective values of the transmitted codes HARD.
It the handset 1 (Fig. 3), the movable contact of the talk witch 152 us normally connected to the standby contact S. When the signal spa US received by the handset 1, the detecting signal RET indicating reception of the signal So is derived from the detecting circuit 162 80 that the microcomputer 140 it place din the mode to check the identi-lying code ID contained in the succeeding code signal CODE.
When the signal Sum it generated by the demodulating circuit 126 and the first word of the code signal CODE it produced by the demodulating circuit 163, the microcomputer 140 -lo-PATENT
checks whether or not the identifying code ID obtained in the code signal CODE matches the identifying code ID set by the switch 155~ It not (i.e., if the call emanates from the base unit 2 of another telephone ~ubscriber3, the microcosm-putter 140 does not carry out the succeeding signal process-in but remains in the standby mode. If the identifying code ID contained in the code signal CODE matches the identifying code ID jet by the switch 155, the particular code HAND 18 checked. In the case of an incoming call, HAND
= WOW is initially established. this means that both handsets lo and lo are specified Jo that the call tone forming circuits 164 of the both handsets lo and I form the bell wound signal. This signal is supplied through the amplifier 127 to the speaker 1~8.
As Fig. I shows, time to follows time if by one word period of the code signal CODE. At time to, the bell wound is produced by both the handsets lo and lo to announce the arrival ox the incoming call (Fig. 7B), In the following description, it is assumed that the handsets lo and lo respectively respond to the incoming call at times to and to. That is, the talk switch 152 is changed in position to the talk contact T t time to in the handset lo fugue ED) and at lime to in the handset lo Fig.
7C). In the handset lo, in response to the movement of the talk switch 152 to the Salk contact T, the signal TX from the microproce~or 140 enable the modulating circuit 113 to generate the FM igloo Sup and the code signal CODE 1 generated by the microcomputer 140. The code goal CODE it converted to the signal Sum by the modulator 161 end then transmitted on the ~lgnal Sup , . ,, .. , . .. . . .. , . .. , ., .. I, . , .. ... ... ... . .. ., .. , .. , " . .. ... ......... .. .. . . .. ... ...
, 122913~ so 2093 he identifying code ID in the code signal CODE
transmitted by the handset lo it derived from the witch 155, and the particular code RAND it derived from the switch 156. the value of the code HAND that indicates transmission from the handset 19 it Winnie. the data signal DATA indicates the response to the reception. As indicated in F1~, 6C, the rode signal CODE is transmitted by the handset lo in two successive word periods beginning at tire I (Fig. ED) and then the transmission is interrupted during two successive word periods. This cycle of alternate transmission and lnterr~ption thereof it repeated. when the second code signal CODE is ended at time to (Fig. ED), the transmission of the signal Sup is stopped by the signal TX. Then, at a time to with a delay of two word periods after the time to, the transmission of the signal Sup it once again enabled by the signal TX and hence the signal CODE is transmitted.
If the talk switch 152 in the handset lo is changed in position to the talk contact T at time I
(shortly after the time to), signal processing exactly same a in the handset lo it carried out. As Fig. 7C shows, the code signal CODE is transmitted from time to. however, in the code signal CODE transmitted by handset lay the value of the particular code HARD is presented a ~01" by the switch 156 (Fig. 3). As Fig. I shows, the tray mission of the code signal COD from the handset lo it such that the transmission of three word periods from the time to i performed and then there it a transmi~ion interruption of two word p~riodQ. This cycle of alternate transmission and interruption thereof is repeated.

13~ S02093 PATENT
Since signals Sup and Sup are simultaneously trays-milted from both handset lo and lo during the period to to to, as Figs. 7C and ED show, if the levels of reception of the signals Sup end Sup axe nearly the same in the base unit 2, radio interference occurs and the base Unlit 2 can not correctly receive the two signals Sup and Sup However, at tome to, the transmission of the .
signal Sup from the handset lo is interrupted over a period of two word periods up Jo time I so that from time to, the base unit 2 becomes able to receive clearly and without radio interference, the signal Sup from the handset lay Since the detection signal RET of the signal Sup is produced by the detecting circuit 262 in the base unit 2 (Fig. 4), the microcomputer 240 is jet in the state to check the succeeding code signal CODE. In Fig. 7, one full wore of the code signal CODE has been received without interference by time to. At that time, the microcomputer 240 checks whether or not the identifying code ID in the code signal CODE matches the identifying code ID set in the witch 255. If they do not match (i.e., the identifying code ID is sent from the handset 1 of another telephone subscriber), the microcomputer 240 does not carry out the succeeding signal processing but is placed in the standby mode. If they do match, the particular code RAND contained in the code signal CODE it checked. In this case, RAND =
~01~ established and specifies the handset lay The base unit 2 tran8mit8 (echoes) once the code signal CODE in which HAND = ~01~ is e~tabli~hed, during the period to to to, a Fig. PA show.

Then, the code signal CODE in which RAND = ~01~ is established it received by both handsets lo and lo, 80 that, at time to the code HAND is produced in both handset lo and lo The codes HAND are respectively checked by the handsets lo and lo. As a Rowley of the checking, in the handset lay HAND = Noel is found to watch the particular code HAND set in the switch 156 Jo that the forming circuit 164 tops forming the bell sound signal A shown in Fig.
7B, the bell sound is terminated at time to. The amplifier 127 is then released from muting by the signal JUTE.
In the handset lo, as a result of the checking, RAND = ~01~ is found not Jo match the particular code HAND
10") set in the switch 156. As Fig. 7B shows, the bell --I . sound is terminated on the handset lo also. At the same : time, the transmission of the signal Sup is terminated in the handset lo, a communication channel having been established between the handset lo an the base 2.
: In the base unit 2, when the transmission of the code signal CODE is ended at time to the amplifier 227 is released from muting by the signal MUTE.
Accordingly, after the time to, only the handset lo carries out transmission 80 that, after lime to, the communication channel between the handset lo and the base unit 2 us normally established, and the handset lo can respond to the incoming call and telephone communication can be made us disclosed above.
In the handset lo, the tr~n~mis~ion of the signal SUP 16 terminated at time to end the LED 166 begin to blink, whereby to announce to the user of the handset lo that the communlcaklon channel with the bate unit 2 it .... . . ...... ....... ..... ............ ... ... .... ... . . .. . . .... . . ...... . .... ... ... . .. . . . ... . .
. .. . .. . . .. . ..

occupied by the handset lay When the connection with thy outside fine I terminated in the handset lay the trays-mission of the signal So in the base unit 2 it stopped and this is detected by the filgnal RET on the handset lo. The LED 166 then tops blinking to announce that the communique-lion channel with the base unit 2 is no longer occupied.
When the handsets lo and lo respond to the lncom-, in call at times to and to as shown in Fig. 7, the handset lo receives the incoming call.
If only the handset lo responds to the incoming call Jay at tome to), or if both handsets lo and lo respond to the incoming call but the radio wave of the handset lo is too weak to cause radio interference, thus, as Fig. 8 shows, the code signal CODE from the handset lo is produced from time to I that, from time to, the code signal CODE, specie lying the handset lay is transmitted. This establishes the communication channel between the handset lo and the base unit 2 from time to.
If only the handset lo responds to the incoming call or if both handsets lo and lo respond to the incoming call but the radio wave of the handset lo is too weak to cause radio interference, then the communication channel between the handset IT and the base unit 2 can be stab-hod similarly.
When an outgoing call us made by the handset l, the following operation it carried out. In the following di6cu~sion, it amid that, in the handsets lo and lo, the talk witches 152 ore changed in position to toe talk contacts T it tomes tl4 and t13, respectively (Fog. Al.
Then, in the handset lay since the witch 152 it connected , -20-~229~3~ so 2093 to the contact T at time t14, on the basis of the output therefrom, the modulating circuit 113 is enabled by the signal TX to transmit the I signal Sup Subsequently, the codes ID and HAND are respectively produced from the switches 155 and 156 Jo that he code signal CODE
containing these codes ID and HAND is transmitted on the signal Sup from time tl4 as shown in Fig. PA. 9 : Also in the handset lo, since the talk witch 152 is connected to the talk contact T at time tl3, the code signal CODE is similarly transmitted on the signal Sup from time tl3, Accordingly, as Figs. PA and 9B show, during the period t14 to t15, the signals Sup and Sup are simultaneously : transmitted from the handset IA and lo so that, on the base unit 2, if the reception levels of the signals Sup and mu are nearly the same, radio interference occurs. Thus the base unit 2 cannot correctly receive either of the signals Sup and Sup : however, from time tl5, when the transmission of :
the signal Sup from tube handset lo is interrupted, the base unit 2 becomes axle to receive the signal Sup from the handset lo without interference.
Consequently during the period t15 to tl8, on operation similar to that performed during the period to to to is carried out. More particular, the base unit 2 trays-mats the code ~lgnal CODE indicative of the code RAND (=

. , , ~01~ specifying the handset lo from time ~16 as shown in Fig 9C, whereby to eatable the commun~catlon channel between the handset lo and the base unit 2 beginning at time .. . . ,, . .... ..... ....... , . . . . -- ..

go S02~93 PATENT
tl8. The amplifier 127 and 227 in the handset lo and the base unit 2 are at the same time released from muting.
Subsequently, when the keyboard 151 is employed in order to key in the telephone number of a third person to be called on the handset lay he microcomputer 140 generates the code signal CODE containing the corresponding dial signal as the data signal DATA. The code goal CODE is ..
converted to the MUSK signal Sum by the modulating circuit 161 end then transmitted Jo the bate unit I At this time, the LED 166 of the handset lo it caused to begin to blink, thus indicating to a user of the handset lo that the communique-lion channel with the base unit 2 it occupied or busy.
In the base unit 2, the demodulating circuit 263 produces the code signal CODE. On the basis of the data signal DATA of the code signal CODE, the forming circuit 264 it controlled by the microcomputer 240 so as Jo form the tone encode signal TO corresponding to the telephone number of the third person to be called. The tone encode signal TO
it supplied through the amplifier 227, the hybrid circuit 231 and the relay circuit 232 to the telephone network line 3. Accordingly, the third person is called. If the third person responds to the call 7 telephone communicate is established as disclosed above.
. When an outgoing call it made from either of the handset lo and lo or even when an outgoing call is made from the both handsets lo and lo but the radio wave of one of them too weak to cause radio interference, the code HAND specifying the handset from which the outgoing I
made it transmitted from the base unit 2 thereby to ..

, . ..... . . . . . .. _ _ _ _ . _ .... _ .

~229134 PATENT
establish a communication channel between the base unit 2 and such handset.
After the communication channel is established between the handsets (for example the handset lay and the base unit 2, if the talk switch 152 of the other handset for example the handset lo) i connected to the talk con act T in order to make an outgoing call, the second outgoing call cannot be completed since the communication channel has already been established between the handset lo and the base unit 2. Thus even if the code signal CODE is transmitted from the handset lo, the responsive code signal CODE is not transmitted from the base unit 2 and in the handset lo the detected signal RET indicating reception of the signal from the base unit 2 it not obtained. Thus, the microcomputer 140 in the handset lo judges that the communication channel is occupied by the handset lay and the LED 166 of the handset lo begins to blink to announce that the communication channel is occupied Figs. lea and lob are flow charts showing the operation of the control circuit 140 of the handsets lo and lo and of the control circuit 240 of the base unit 2 in response to an incoming call.
In jig. lea, position 101 of a program 100 repro-sent the program start, in which the handset $6 in the standby mode. it step 102, a check is made to determine whether or not the E~gnal So has been received prom the base unit 2. (Compare step 203 in Fig. lob.) If not, the program loops back Jo that the check is made repeatedly.
When the signal So us received, the ID code it derived in step 103, and, in step 104, check ivy made to determine ... , ..... ,, .. . ... , ., , . , , . , ...... ,, . , , . . , ..... , . , , ., . .. . _ ., . . _. _ ..
.....

SLY

PATENT
whether or not the ID code matches that representing the combination ox the base unit 2 and the handsets lo and lo.
If not, the program loops back to step 102. If a match is found, the RAND code it derived at lop 105, and, at step 106, a determination it made whether or not the HAND code is common to both handsets (00) or proper to the handset in which the program is being carried out. If neither match us found, the program loops back to step 102. If the RAND code is common to both handsets ox proper to the handset in which the program is being carried out, the ringing signal is e tablished at step 107, and, at step 108, a determination is made whether or not the witch 152 has been placed in the talk position. If not, the program loops back to step 102.
It the determination made at atop 10~ us that the switch 152 has been placed in the talk position, the signal Sup is transmitted to the base 2 at step lo.
At step 110, a determination is made whether the signal So has been echoed by the base. (Compare step 206 in Fir lob.) If not, the program loops back to step 109, and the signal Sup continues to be transmitted. If the signal So 16 found at step 110 to have been echoed by the base, the HIND code is derived at step 111, and, at step 112, a determination is made whether or not the RAND code is proper to the handset in which the program it Boolean carried out.
If not, the handset stops transmitting the signal Sup to the base, the ringing signal tops, and the LED 166 is lighted at step 114. At step 115, a determination is jade whether the RET final 15 present. If jot, the program loops back to step 114. If it it present, the LED 166 is turned off, and the program loops back to step 102.

If at step 112 the code HARD us found to be correct, eye., is found to math the code HAND in which the program it being carried out, the ringing signal stops and the mute is released at step 113, and the telephone mode is established. The program end it indicated at 150.
In Fig. lob, position 201 of a program 200 repro-sets the program start, in which the base unit 2 is in thy standby mode. The program repeatedly checks at step 202 for an incoming call from a third person. As long as no such call is received the program loops back. If an incoming call it received from a third person, the signal So is transmitted to both handsets lay lo at step 203. When, as a result of step 109 of Fig. lea the signal Sup is transmitted . .
to the base unit 2, the signal Sup is received by the base unit at step 204. At step 205, the code HANK it stored in the RAM 243. At step 206, the base unit 2 transmits (etch-owes) the signal So. This is detected at step 110 in Fig.
lea. A step 207, the mute is released, and at step 208, the handset is connected to the telephone fine. The program end it indicated at 2090 In Fog. AYE, position 301 of a program 300 repro-sets the program start, in which the handset 1 is in the standby mode. The program checks at step 302 whether or not the witch 152 has been placed in the talk position. If not, the program continually loops back. If at step 302 the witch 1~2 it found to have been placed on the talk position, then, at Flop 303 the signal Sup it tran~itted to the be e unit 2. At step 304, a determination it made whether or not the signal So ha been received from the base 2. If not, the program loops back to step 303, and the ~2;~9~4 PATENT
signal Sup is retransmitted. If the signal So (echo) from the base 2 it detected at step 304, the HAND code is derived at Beep 305. At step 306, a determination is made whether or not the HAND code i correct. If it is incorrect, then, at step 308, the handset stops transmitting the signal Sup to the base I and the LED 166 it turned on. Then, at step 309, a check us made for the existence of the RET signal..
If it is not found, the program loops back to step 308. If it is found, the LED 166 it turned off, and the program loops back to step 302.
If at step 306 the HAND code is found to be correct, the mute is released at step 307, and the telephone mode is established. This brings the program to the end 350.
Before an outgoing call is made by the handset 1, the base unit 2 is initially in the program Tart position or standby mode 401 of a program 400 (Fig. 12B). At step 402, a determination is jade whether the signal Sup has been received from the handset. (compare step 303 in Fig. AYE.) If not, the program loops back. When the signal Sup it transmitted (step 303 of Fig. Allah, the heck performed it step 402 results in a determination that the signal has been received. The ID code it then derived at step 403. At step

4~4, a determination is made whether or not the ID code 8 correct. If not, the program loops back to step ~02. If the ID code it correct, the HAND code is derived at rep 405 and stored in the RAM 243 at Beep ~06. The slgn~l By is transmitted at step 407 (eschew The jute it released at step 408, and the handset is connected to the telephone line ~29~3~ S02093 PATENT
3 to establish the telephone mode at step 409. this brings the program to the program end 450.
Thus according to the invention, when the base unit 2 is used combination with two handsets lo and lo, either of the handsets lo end lo can correctly receive an incoming call or place an outgoing call. Even if an attempt is made to use both of the handsets lo and lo simultaneous-lye one will be we elected and will establish a comma-nicatlon channel with the outside line 3 without radio interference from the other.
While in the above-described embodiment the base unit 2 is used in combination with two handsets lo and lo, three or more handsets may optionally be used in combination with a jingle base unit. In the case of three handsets lay I and lo, the particular code HAND of two bits of the code signal CODE as shown in Fig. 5 is owe: code common to handsets lay lo and lo "01~: code pertaining to the handset lo ~10~: code pertaining to the handset lo code pertaining to the handset lo In this case the code signal CODE is repeatedly transmitted from the base unit 2 at one word intervals as shown in Fig. loan The code signal CODE it transmitted from the handset lo as shown on Fig. lob That it, it is onion-uou~ly transmitted four limes (four words), end the triune mission whereof it interrupted for nun interval of three word. This operation 1B repeated. the code signal CODE it transmitted from the handset lo I shown on Fog. lQC. what I, it it transmitted continuously three time and then interrupted for an interval of three word, and this owe A
~02093 PATENT
operation is repeated. The code signal CODE is transmitted from the handset lo as shown in Fig. lode That it, it is continuously transmitted twice, and then the transmission thereof is interrupted for an interval of three words. This operation is repeated. Thus, the three handset lay lo and lo can be used in a manner similar Jo the manner on which the two handsets lo and lo are used. Of course, if more .
that your handsets 1 ore used, the number of bits in the rode signal HAND is increased, and the format of Fig. 5 is changed core pondingly. Upon transmission my the handset 1, the code signal CODE it transmitted continuously a predetermined number of times and the transmission thereof is interrupted during an interval corresponding to the above-described predetermined time. The format it such that the transmission of each of the particular codes periodical-lye corresponds to non-transmission of all of the other particular codes of the remote units, whereby each of the particular codes can periodically be received by the base unit 2 without interference caused by transmission of the other particular codes of the remote units.
The operation of the circuits 161 to 163 and 261 to 263 was well as the circuits 140 and 240) can be realized by software. Further, the telephone number of a third per&on can be delivered a a dial pulse.
If the transm~tter-receiver is of a carrier wave type in which a jingle be e unit is employed with a plural-try of remote units, the invention can be applied not only to a cordless telephone but Lowe to a transceiver and an inter phone system of a carrier wave type using a commercial AC power line I

PATENT
s it forth above, according to the inYen~ion, when a single base unit us employed with more than one remote unit, a plurality of remote unit can be placed in the talk mode simultaneously without radio interference 80 that a selected one of the remote apparatus can be correctly connected with the outside line.
Thus there is provided in accordance with the .
invention a novel and highly-effective apparatus for stab-fishing radio communication between a base unit and a plurality of remote units without risk of radio interfere once. Many modifications of the preferred embodiment of the apparatus disclosed above will readily occur to those skilled in the art. For example, the frequencies employed, the number of handsets employed in combination with a single base unit, and the particular format employed to ensure that each of the particular codes can be periodically received by the base unit without interference caused by transmission of the other particular codes of the remote units can all be varied within wide limits. Accordingly, the invention is to be construed as including all structure writhing the scope of -the appended claims.

Claims

1. Apparatus comprising a base unit and a plurality of remote units, said remote units being respec-tively adapted to establish radio communication at separate times with said base unit;
each of said remote units comprising:
means for generating a particular code in a particular format that includes at least one interval in which said particular code is present and at least one interval from which said particular code is absent, the particular code and particular format of each remote unit being different from those of the other remote units of said plurality of remote units, and means for transmitting said particular code in said particular format to said base unit;
said particular formats being such that the transmission of each of said particular codes periodically corresponds to non-transmission of all of the other particu-lar codes of said plurality of remote units, whereby each of said particular codes can be periodically received by said base unit without interference caused by transmission of the other particular codes of said plurality of remote units;
said base unit comprising means for echoing the particular cod transmitted by a selected one of said remote units; and each of said remote units further comprising means for detecting whether or not its own particular code matches said particular code echoed by said base unit;

and further comprising means responsive to such a match for establishing a communication channel between said base unit and the one of said plurality of remote units in which such match occurs, said communication channel while established precluding establishment of a communication channel between said base unit and any other of said plural-ity of remote units. .

2. Apparatus according to claim 1; wherein each of said remote units is a cordless telephone.

3. Apparatus according to claim 2; wherein each of said remote units comprises means for generating an up channel audio signal, frequency modulator means responsive to said up channel audio signal for generating a frequency modulated up channel signal, and antenna means response to said frequency modulated up channel signal for transmitting said frequency modulated up channel signal to said base unit.

4. Apparatus according to claim 3; wherein each of said remote units further comprises control means for generating a code signal including said particular code and minimum shift keying modulating means response to said code signal for generating a modulated audio frequency code signal, said frequency modulator means being responsive to said modulated audio frequency code signal, whereby said audio frequency code signal is frequency modulated for transmission to said base unit.

5. Apparatus according to claim 4; wherein each of said remote units further comprises keying switch means connected to said control means for keying in the number of a third person to be called.

6. Apparatus according to claim 4; wherein each of said remote units further comprises talk switch means connected to said control means for selectively placing said control units in a standby mode or a talk mode.

7. Apparatus according to claim 4; wherein each of said remote units further comprises channel switch means connected to said control means for selecting one of a plurality of channels for communication with said base unit.

8. Apparatus according to claim 4; wherein each of said remote units further comprises first dip switch means connected to said control means for generating an identifying code unique to the combination of said base unit and said remote units.

9. Apparatus according to claim 4; wherein said means in each said remote units for generating said particu-lar code comprises second dip switch means connected to said control means.

10. Apparatus according to claim 4; wherein said base unit comprises means for generating a down channel audio signal, frequency modulator means responsive to said down channel audio signal for generating a frequency mod-ulated down channel signal, and antenna means responsive to said frequency modulated down channel signal for transmit-ting said frequency modulated down channel signal to said base units.

11. Apparatus according to claim 10; wherein said base unit further comprises control means for generating a code signal selectively including the particular code of one of said remote units or a code common to all of said remote units and minimum shift keying modulating means responsive to said code signal for generating a modulated audio fre-quency code signal, said frequency modulator means in said base unit being responsive to said modulated audio frequency code signal in said base unit, whereby said audio frequency code signal in said base unit is frequency modulated for transmission to said remote units.

12. Apparatus according to claim 11; wherein said base unit further comprises channel switch means connected to said control means in said base unit for selectively placing said base unit in one of a plurality of channels for communication with said remote units.

13. Apparatus according to claim 11; wherein said base unit further comprises third dip switch means connected to said control means in said base unit for generating an identifying code unique to the combination of said base unit and said remote units.