JPH0681095B2 - Cordless telephone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial Field B Outline of the Invention C Conventional Technology D Problems to be Solved by the Invention E Means for Solving Problems (FIG. 1) F Action G Example G ₁ First Example ( (Figs. 1 to 6) G ₂ Other Embodiments H Effect of Invention A Field of Industrial Application This invention relates to a cordless telephone.

B Outline of the Invention The present invention is designed to send an identification code from a base unit to a handset through a contact and an identification code from a handset to a base unit through a communication channel when an identification code (ID code) is set in a cordless telephone. The identification code can be set in the handset in a stable and reliable manner.

C Conventional Technology In a general telephone, its telephone cord is connected to a rosette attached to a pillar or a wall. Therefore, the range in which the telephone can be moved is about several meters depending on the length of the telephone cord. However, if the phone cord is lengthened to increase the range of movement, the cord will become entangled or obstructed.

Therefore, in the United States and the like, a telephone system called a cordless telephone is considered.

As shown in FIG. 4, this is composed of a transceiver (1) called a handset and a transceiver (2) called a base unit, and a telephone line (3) is connected to the base unit (2). Together with the base unit (2)
The handset (1) and the handset (1) are coupled to each other by radio waves, and the telephone of the subscriber is handled in the same manner as a general telephone.

Therefore, the subscriber can freely move the handset (1) when making a call, and the telephone cord is not tangled or disturbed.

The distance (service area) where the handset (1) can be separated from the base unit (2) is about 300 m. The frequency of the radio wave used between the handset (1) and the base unit (2) is 49MHz band for the up channel and 46MHz band for the down channel, and 10 duplex channels are approved by the FCC (the numerical value is Provisional value).

Thus, according to this cordless telephone, the telephone can be conveniently used.

However, in this cordless telephone, since the handset (1) and the base unit (2) are connected by using radio waves, when there is another cordless telephone in the vicinity, the person who makes the call is the caller. Since a communication channel is formed between the handset (1) of the subscriber A and the base unit (2) of another subscriber B, the telephone charge which the subscriber A would otherwise have to pay is B will be billed and billed.
Alternatively, when the subscriber A is making a call through his / her handset (1) and the base unit (2), the subscriber B may be able to eavesdrop on the content of the call.

Therefore, in an actual cordless telephone, an identification code (ID code) is given to the handset (1) and the base unit (2). That is, this identification code is the same code for the handset (1) and the base unit (2), and one of "0" to "255" represented by an 8-bit binary code is selected, for example. . Then, when communication is started between the handset (1) and the base unit (2), first, the identification code is transmitted from one side to the other side, and whether the received identification code matches the own identification code. I will be checked. Then, if they match, the communication channel is formed thereafter, and the subscriber can use the telephone, but if they do not match, the communication channel is not formed.

FIG. 5 shows an example of a cordless telephone handset (1) which uses such an identification code, in which (110) is a transmitting circuit and (120) is a receiving circuit. Further, FIG. 6 shows an example of a similar base unit (2), in which (210) is a transmitting circuit and (220) is a receiving circuit.

Then, at the time of transmission, in the handset (1), the audio signal St from the transmitter (111) is changed to the low frequency amplifier (112).
Is supplied to the FM modulation circuit (113) through the FM channel and is converted into an FM signal Su of the up channel, and this FM signal Su is passed through the high frequency power amplifier (114) and the band pass filter (115) whose pass band is the up channel to the antenna ( 100) and sent to the base unit (2).

Then, in the base unit (2), the signal (radio wave) Su from the handset (1) is received by the antenna (200), and the received signal Su is a bandpass filter (221) having an up channel as a pass band and It is supplied to the mixer circuit (223) through the high frequency amplifier (222), and the local oscillation signal of a predetermined frequency is supplied from the local oscillation circuit (224) to the mixer circuit (223) to convert the signal Su into an intermediate frequency signal. , The intermediate frequency signal is supplied to the FM demodulation circuit (226) through the intermediate frequency amplifier (225) to demodulate the audio signal St, and the signal St is converted into the low frequency amplifier (227).
→ 2-line to 4-line conversion circuit (231) → It is sent to the telephone line (3) through the signal line of the relay circuit (232).

In this case, the relay circuit (232) is a relay for turning on / off the connection between the base unit (2) and the telephone line (3), and temporarily holds a call after the base unit (2) and the line (3) are connected. It has a hold relay for holding the line (3) when it is interrupted.

In addition, when receiving a voice signal Sr from the telephone line (3)
Is supplied to the handset (128) of the handset (1) by the same processing as when transmitting. That is, the voice signal Sr from the line (3) is converted into the relay line (232) → the conversion circuit (231).
→ It is supplied to the FM modulation circuit (213) through the signal line of the low frequency amplifier (212) and converted into the FM signal Sd of the downlink channel of the same channel as the FM signal Su, and this signal Sd is converted to the high frequency power amplifier (214) and It is supplied to the antenna (200) through a band pass filter (215) having a pass band in the downlink channel and transmitted to the handset (1).

Then, in the handset (1), the signal Sd from the base unit (2) is received by the antenna (100), and the received signal Sd is a bandpass filter (121) having a downlink channel as a pass band and a high frequency amplifier ( 122)
Is supplied to the mixer circuit (123) through the local oscillation circuit (124) and a local oscillation signal of a predetermined frequency is supplied to the mixer circuit (123) to convert the signal Sd into an intermediate frequency signal. The audio signal Sr is demodulated by being supplied to the FM demodulation circuit (126) through the intermediate frequency amplifier (125), and this signal Sr is supplied to the receiver (128) through the low frequency amplifier (127).

Further, in the handset (1), reference numeral (140) represents a control circuit for controlling a communication channel and the like. The control circuit (140) is composed of a one-chip type microcomputer. For example, (141) is a CPU for 4-bit parallel processing, (142) is a ROM in which a program is written, and (143) is Work area RAM, (144) is an input port, and (145) is an output port.

The microcomputer (140) has a dial key (151),
The talk switch (152) and the channel switch (153) are connected. In this case, the dial key (151) is a non-lock type push switch for inputting the telephone number of the other party, and the talk switch (152) is a three-position switch for selecting the operation mode of this handset (1). The switch (152) is contact O
At the time of, the power supply of the circuits other than the microcomputer (140) is turned off (off mode), at the contact S, it is in a standby state (standby mode) for receiving the signal Sd from the base unit (2), and at the contact T. , The handset (1) and the base unit (2) are in a communication state (talk mode), and are normally connected to the standby contact S.

The switch (153) is a non-lock type push switch for changing the communication channel, and the outputs of these keys and the switches (151) to (153) are supplied to the microcomputer (140).

Further, (161) shows an MSK modulation circuit, which converts a code signal from a binary signal to an MSK signal Sm when a code signal such as an identification code ID and a dial signal DS is supplied from the microcomputer (140). The signal Sm is supplied to the amplifier (112).

Further, (162) indicates a reception detection circuit, which is connected to the demodulation circuit (126), and which receives the signal S from the base unit (2).
The presence or absence of the signal Sd is detected by utilizing the fact that the frequency component of the output of the demodulation circuit (126) differs depending on the presence or absence of d, and the detection signal SDET is supplied to the microcomputer (140).

Further, (163) indicates an MSK demodulation circuit, which is connected to the demodulation circuit (126) and demodulates a code signal from the MSK signal Sm sent from the base unit (2). Supplied to the microcomputer (140).

Further, (164) indicates a call tone forming circuit, which is controlled by the microcomputer (140) to form a ring tone signal (ring tone signal) when a call is received. The ring tone signal is a ringer signal. (165).

Further, a signal CH designating a channel is supplied from the microcomputer (140) to the modulation circuit (113) and the local oscillation circuit (124), and a signal TX for controlling whether or not the FM signal Su is sent is supplied to the modulation circuit ( 113). In addition, the muting signal MUTE is sent from the microcomputer (140) to the amplifier (127).
Is supplied to.

Further, in the base unit (2), (240) indicates a control circuit. The control circuit (240) is configured similarly to the control circuit (140) of the handset (1) and has the same function, and the circuit (141) of the control circuit (140).
For the circuits corresponding to (145), replace the numbers in the 100s
Numbers in the 200s are attached and explanations are omitted.

The switches (253) and circuits (261) to (264) are also the switches (153) and circuits (161) to (161) of the handset (1).
Since it is the same as that of (164) and is the same for each signal, description thereof will be omitted. However, the forming circuit (26
4) forms a tone-encoded signal (DTMF signal) TE corresponding to the telephone number when calling the other party.

Further, (265) shows a bell sound signal detection circuit (ring detector), which is connected to the telephone line (3) and detects a bell sound signal when a call is received. Is supplied to the microcomputer (240).

When making a call from the handset (1) to the other party, the following operations are performed by the microcomputers (140) and (240) according to the programs of the ROMs (142) and (242).

That is, when the talk switch (152) is set to the talk contact T, the modulation circuit (11
The sending of the FM signal Su from 3) is permitted, the unmodulated signal Su is sent, and then the identification code ID is extracted from the RAM (143), and this code ID is sent to the MSK by the modulation circuit (161).
The signal Sm is supplied to the amplifier (112). Therefore,
The identification code ID is transmitted to the base unit (2) by the FM signal Su.

Then, in the base unit (2), when the signal Su is received, the detection signal SDE of the signal Su from the detection circuit (262).
Since T can be obtained, the microcomputer (240) continues the identification code ID
Enter the check state of. Then, the signal Sm is extracted from the demodulation circuit (226) and the identification code I is output from the detection circuit (263).
When D is retrieved, it is checked if this code ID matches the identification code ID stored in RAM (243) and if it is incorrect (from another subscriber's handset (1)) then However, when it is correct, the signal TX allows the sending of the FM signal Sd from the modulation circuit (213) to establish the communication channel, and the signal MUTE causes the amplifier (227) to operate. Muting is canceled.

Further, at this time, the signal Sd is transmitted to extract the signal SDET from the detection circuit (162) in the handset (1), which is detected by the microcomputer (140) and the muting of the amplifier (127) is performed by the signal MUTE. It will be canceled.

Then, in the handset (1), dial key (15
When 1) is operated according to the telephone number of the other party, the corresponding dial signal DS is formed by the microcomputer (140) and converted into the MSK signal Sm by the modulation circuit (161), and similarly the base unit (2) Sent to.

Then, in the base unit (2), the dial signal DS is taken out from the demodulation circuit (263), and this signal DS
Based on, the formation circuit (264) is controlled by the microcomputer (240) to form a tone encode signal TE corresponding to the telephone number of the other party, and this signal TE is passed through the amplifier (227),
Further, it is sent to the telephone line (3) through the conversion circuit (231) and the relay circuit (232). Therefore, if the other party is called by this signal TE and the other party answers the telephone, then the call becomes possible as described above.

On the other hand, when a call is received from the other party, the following operation is performed.

That is, normally, the talk switch (152) is connected to the standby contact S, but when the call comes from the other party, the bell sound signal BL is taken out from the detection circuit (265) and supplied to the microcomputer (240). , A signal TX based on this
The sending of the FM signal Sd of the modulation circuit (213) is permitted by this, and then the identification code ID of the RAM (243) is sent to the modulation circuit (26
1) is converted into a signal Sm, and this signal Sm is converted into an amplifier (21
2) and thus the identification code ID is transmitted to the handset (1) by the FM signal Sd.

Then, in the handset (1), when the signal Sd is received, the signal SDET is extracted from the detection circuit (162) and supplied to the microcomputer (140), and the microcomputer (140) enters a check state of the identification code ID. When the identification code ID is extracted from the demodulation circuit (163), this code ID and RAM (1
It is checked that the ID code stored in 43) matches the ID code. If it is not correct, no further processing is performed.
While the standby state is continued, when it is correct, the transmission of the FM signal Su from the modulation circuit (113) is permitted by the signal TX to establish the communication channel, and at the same time, the bell sound signal is formed in the formation circuit (164). A signal is sent to the ringer (165) and a bell rings, signaling that the call is coming. Therefore, if the switch (152) is switched to the talk contact T, then the speaker (128)
The bell sound from the computer stops, and the amplifiers (127), (22
The muting of 7) is canceled by the signal MUTE, and the call becomes possible as described above.

The above is the basic configuration and operation of the cordless telephone using the identification code.

According to this cordless telephone, if the identification codes match, a communication channel is formed thereafter, and the subscriber can use the telephone. If they do not match, the communication channel is not formed. There is no problem that the telephone charge of the person A is charged to the subscriber B or is wiretapped.

(Reference: Specification and Drawing of Japanese Patent Application No. 59-21259) D Problems to be Solved by the Invention However, when this identification code is used, a problem occurs in the setting circuit of the identification code.

That is, the handset (1) is naturally cordless, and has a built-in battery as a power source. Then, even when the handset (1) is not in a call, a part of the circuit is energized and working in case of a call. For this reason, if the power source battery is a general dry battery, the running cost is high, so the power source battery is a rechargeable battery such as a nickel-cadmium battery, and when the battery becomes empty, as shown in FIG. By setting the handset (1) at a predetermined position of the base unit (2), the battery contained in the handset (1) is charged from the power supply circuit of the base unit (2).

Therefore, if the identification code is stored in the memory of the handset (1), the identification code disappears when the battery runs out. Therefore, when the battery of the handset (1) is charged, the identification code of the handset (1) The identification code needs to be reset or updated.

The present invention is intended to ensure that when the identification code of the handset (1) is reset or updated, it can be performed reliably and stably.

E Means for Solving Problems In the present invention, when the handset (1) is set on the base unit (2) as shown in FIG. 3, (i) the base unit (2) changes to the handset (1). An identification code is sent through a contact (terminal).

(Ii) When the handset (1) receives the identification code, the handset (1) stores the identification code in the memory and returns it to the base unit (2) through the communication channel.

(Iii) The base unit (2) confirms the returned identification code.

The processing is called.

F Action When the battery of the handset (1) is charged, the identification code of the handset (1) is automatically reset or updated.

G Embodiment G ₁ First Embodiment In the base unit (2) of FIG. 1, (272) is a power supply circuit, which has a power transformer and a rectifier circuit, and has a commercial AC through the power plug (271). A voltage is supplied to form a predetermined DC voltage. Then, this DC voltage is supplied to each part of the base unit (2) as its operating voltage and is also supplied to the charge output contact (277) through the charge detection circuit (273). This detection circuit (273)
Detects the charging current flowing through the contact (277), and the detection output is supplied to the interrupt input INT of the microcomputer (240). Further, the port output terminal Q ₀ of the microcomputer (240) is connected to the output contact (278). In addition,
(279) is a common contact (ground contact).

Further, in the hand unit (1), (172) is a rechargeable battery, and the output voltage thereof is supplied to each part of the handset (1) as its operating voltage. Further, (174) is a charging circuit, which charges the battery (172) with the charging voltage when the charging voltage is supplied to the charging input contact (177). Further, (173) is a charge detection circuit, which detects when a charge voltage is supplied to the contact (177), and the detection output is interrupted by the microcomputer (140) through the delay circuit (175). Supplied on input INT. In this case, the delay time in the delay circuit (175) is the battery (172).
Is a little longer than the period until the terminal voltage becomes stable and each part operates normally due to the floating charge.

The input contact (178) is connected to the port input terminal Q _I of the microcomputer (140). Note that (179) is a common contact, and the contacts (177) to (179) and the contacts (277) to (279) are provided at positions where they contact each other when the battery (172) is charged.

Further, the ROM (142) is provided with an interrupt subroutine (10) as shown in FIG. 2, and the ROM (242) is provided with an interrupt subroutine (20).

According to such a configuration, since the battery (172) is charged, when the handset (1) is set at a predetermined position of the base unit (2) as shown in FIG. 3, as shown in FIG. , Contacts (177) to (179) and contacts (277) to (2
79) and each contact. Therefore, power supply circuit (272)
The DC voltage from the battery (17) passes through the line of the detection circuit (273) → contact (277) → contact (177) → charging circuit (174).
2) and the battery (172) is charged.

Then, in the base unit (2), the terminals (27
When the charging current flows through 7), this is detected by the detection circuit (273), and the detection output interrupts the CPU (241).

When this interrupt occurs, the subroutine (20) starts from step (21), and a delay (waiting time) of a predetermined period is performed in step (22). The delay time in this step (22) is set to be slightly longer than the delay time in the delay circuit (175). Therefore, at the time when this step (22) is completed, the handset (1) is charged by floating charging. Each part is already operating normally.

Then, the processing of the CPU (241) moves to step (23), and a new identification code ID is formed, for example, by a random number, and then the new identification code ID is output to the port output terminal Q ₀ in step (24). The identification code ID is supplied to the port input Q _I of the microcomputer (140) through the contacts (278) and (178).

Further, the processing of the CPU (241) proceeds to step (25), and the identification code ID returned from the handset (1) is received. In this case, as will be described in the routine (10), the return of the identification code ID is performed through the up channel as in the case of the identification code ID at the time of a call, and therefore is returned from the demodulation circuit (163). The identification code ID is retrieved. And this identification code
When the ID is retrieved, the process then proceeds to step (26), where the returned identification code ID is the identification code formed in step (23).
If it is equal, the process proceeds from step (26) to step (27), and the new identification code ID formed in step (23) is stored in RAM (243).
The end code indicating the end of this routine (20) is supplied to the port input terminal Q _I of the microcomputer (140) through the contacts (278) and (178) from the port output terminal Q _{0 in} step (28). Then, the routine (20) is ended by the step (29).

When the identification code ID returned in step (26) is not equal to the identification code ID formed in step (23), the process proceeds from step (26) to step (3).
The process proceeds to 1), the code indicating the retransmission of the identification code is supplied from the port output terminal Q ₀ to the port input terminal Q _I , and then the process returns to step (23).

Therefore, steps (23) to (26) and (31) are repeated until the identification code ID formed in step (23) is returned, and the identification code ID formed in step (23) is returned.
Is sent back, the identification code ID is stored in the RAM (242) in step (27).

On the other hand, in the handset (1), when the contact (177) and the contact (277) are connected to increase the voltage of the contact (177), this is detected by the detection circuit (173) and the detection output is delayed. The circuit (175) is delayed until each part of the handset (1) operates normally, and the delayed output interrupts the CPU (141).

When this interrupt occurs, the subroutine (10) starts from step (11), and in step (12), the new identification code ID supplied to the port input terminal Q _I in step (24) is fetched, and then in step (12). In 13), the new identification code ID is stored in RAM (143),
Then, in step (14), the new identification code ID stored in step (13) is returned to the base unit (2). In this case, this identification code ID will be returned in the same manner as the identification code ID when making a call.
Converted to K signal Sm, and further up channel FM signal Su
Is transmitted to the base unit (2) by the.

Subsequently, the processing of the CPU (141) proceeds to step (15), where the end code or retransmission code supplied to the port input terminal Q _I in step (28) or (31) is fetched, and then in step (16). Whether the fetched code is an end code or a resend code is checked. When the end code is the end code, the process proceeds to step (17) to end this routine (10). When the end code is the resend code, the process is ended. Return to step (12), and then step (12) ~
(16) is repeated.

Thus, according to the present invention, when the handset (1) is set on the base unit (2) to charge the battery (172) of the handset (1), the identification code ID is updated or reset, but in this case, If a new identification code ID is sent from the base unit (2) to the handset (1), it will be returned from the handset (1) to the base unit (2) and checked, so an incorrect identification code will be sent to the handset (1) due to an error. The ID is never set.

Moreover, in this case, in particular, according to the present invention, when the identification code ID is sent from the base unit (2) to the handset (1), it is sent through the contacts (278) and (178), and the handset (1) is sent to the base unit (2). ) Is sent through the communication channel, so access to the identification code ID is stable and reliable.

That is, when the identification code ID is sent from the base unit (2) to the handset (1) and when the identification code ID is returned from the handset (1) to the base unit (2), both access through a contact,
Both can be considered as a method of accessing through a communication channel. However, when both are accessed through contacts, contacts (177) and (277) for charging and contacts (178) and (278) for sending an identification code ID from the base unit (2) to the handset (1). ), A contact for returning the identification code ID from the handset (1) to the base unit (2), and a common contact (179), (279). Then, it is not possible to expect that all of the four sets of contacts will surely come into contact with each other only by placing the handset (1) on the base unit (2), and contact failure may occur. Therefore, both of them are unstable in terms of connection when they are accessed through the contacts.

Also, when accessing both via a communication channel, if there is a cordless telephone of the same channel in the vicinity, that cordless telephone may respond, failing to access the identification code or using another cordless telephone. The identification code may be set on your handset.

However, according to the present invention, when the identification code ID is sent from the base unit (2) to the handset (1), it is sent through the contacts (278) and (178), and the handset (1) is sent.
Since the return from the base unit to the base unit (2) is sent through the communication channel, the contacts are contacts (177) to (179),
Three pairs (277) to (279) are sufficient and stable. Also, since the communication channel is used for returning the identification code ID from the handset (1) to the base unit (2),
It is reliable and unaffected by nearby cordless telephones.

Furthermore, when the identification code ID is accessed by making the contacts (178), (278) bidirectional, the peripheral direction must also be bidirectional or the direction can be switched, which leads to complexity and cost increase. However, according to the present invention, the contact (17
8) and (278) and their peripheralization may be unidirectional, simple and low cost.

G ₂ Second Example In the above, when sending a new identification code ID,
If a free communication channel is searched for, the data of this free channel is also sent in step (24), and the access in steps (14) and (25) is performed by that free channel, it is more stable and reliable. Become.

Further, in the above description, the identification code ID is transmitted / received only by establishing the communication channel, but the identification code ID may be always transmitted / received using the outside of the band of the signals Sr, St even after the communication channel is established.

H Effect of the Invention According to the present invention, the battery (172) of the handset (1)
When the handset (1) is set on the base unit (2) to charge the battery, the identification code ID is updated or reset, but in this case, a new identification code ID is sent from the base unit (2) to the handset (1). Then, since this is returned from the handset (1) to the base unit (2) and is checked, an incorrect identification code ID is not set in the handset (1) due to an error.

Moreover, in this case, in particular, according to the present invention, when the identification code ID is sent from the base unit (2) to the handset (1), it is sent through the contacts (278) and (178), and the handset (1) is sent to the base unit (2). ) Is sent through the communication channel, so access to the identification code ID is stable and reliable.

That is, when the identification code ID is sent from the base unit (2) to the handset (1) and when the identification code ID is returned from the handset (1) to the base unit (2), both access through a contact,
Both can be considered as a method of accessing through a communication channel. However, when both are accessed through contacts, contacts (177) and (277) for charging and contacts (178) and (278) for sending an identification code ID from the base unit (2) to the handset (1). ), A contact for returning the identification code ID from the handset (1) to the base unit (2), and a common contact (179), (279). Then, it is not possible to expect that all of the four sets of contacts will surely come into contact with each other only by placing the handset (1) on the base unit (2), and contact failure may occur. Therefore, both of them are unstable in terms of connection when they are accessed through the contacts.

Also, when accessing both via a communication channel, if there is a cordless telephone of the same channel in the vicinity, that cordless telephone may respond, failing to access the identification code or using another cordless telephone. The identification code may be set on your handset.

However, according to the present invention, when the identification code ID is sent from the base unit (2) to the handset (1), it is sent through the contacts (278) and (178), and the handset (1) is sent.
Since the return from the base unit to the base unit (2) is sent through the communication channel, the contacts are contacts (177) to (179),
Three pairs (277) to (279) are sufficient and stable. Also, since the communication channel is used for returning the identification code ID from the handset (1) to the base unit (2),
It is reliable and unaffected by nearby cordless telephones.

Furthermore, when the identification code ID is accessed by making the contacts (178) and (278) bidirectional, the peripheral circuit must also be bidirectional or the direction can be switched, resulting in complexity and cost increase. However, according to the present invention, the contact (17
8) and (278) and their peripheralization may be unidirectional, simple and low cost.

[Brief description of drawings]

FIG. 1 is a system diagram of an example of the present invention, and FIGS. 2 to 6 are diagrams for explaining the same. (1) is the handset, (2) is the base unit, (11
0) and (210) are transmission circuits, (120) and (220) are reception circuits, and (140) and (240) are control circuits.

Claims (1)

[Claims] 1. A handset and a base unit connected to a telephone line, wherein communication between the handset and the base unit is performed by radio waves, and the handset and the base unit are distinguished from each other. The code is transmitted, and the transmitted identification code is checked on the other side, and the communication channel between the handset and the base unit is established only when the transmitted identification code is correct. In the telephone, the handset and the base unit, when the handset is set to a predetermined position of the base unit, contact points are provided to contact each other, when the handset is set to the predetermined position of the base unit, From the above base unit An identification code is supplied to the handset through the contact point, the supplied identification code is stored in the handset, and is returned from the handset to the base unit through the communication channel, and the returned identification code is the handset. A cordless telephone which is compared and checked with the identification code supplied to, and when the both identification codes are equal, the communication is performed using the identification code thereafter.