JP2806788B2 - Cordless telephone relay system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cordless telephone relay system.

[0002]

2. Description of the Related Art An example of this type of conventional cordless telephone relay system is disclosed in Japanese Patent Application Laid-Open No. 61-72422 entitled "Cordless Telephone Relay System". The contents will be described with reference to the drawings.

FIG. 2 is a block diagram showing a conventional example disclosed in JP-A-61-72422.

Incoming call operation In FIG. 2, when a subscriber (not shown) dials the telephone number of the cordless telephone 8, a call bell signal arrives at the connection device 7 from the telephone office. The ringing bell signal is output from a 2-wire to 4-wire conversion circuit (H) 7
1, via the control circuit (CNT) 72, the transmission circuit (T) 7
It is sent by radio frequency f ₁₁ by 4. In the cordless relay telephone 9, the incoming call is detected by the receiving circuit (R) 91 and the control circuit (CNT) 93. Control circuit (C
Thus, the NT 93 issues a visible or audible signal to notify the subscriber. As a result, the subscriber can transmit and receive the signal (T
R) 94 can be removed from a hook (not shown) to answer the call as in a conventional cordless telephone system.
However, in this case, the control circuit (CNT) 97 connects the busy notification melody sound source 96 and the transmission circuit (T) 98
The by driven to, by a radio wave of a frequency f _13, via the frequency converter 81 that cordless relay telephone 9 is in use, and notifies the next order cordless telephone.

If the subscriber does not answer, the ringing bell signal passes through another contact of the hook switch (FS) 95 and the control circuit (CNT) 97 and the transmission circuit (T) 9
8 route and sent is converted into radio frequency f _13.

[0006] Then the reception frequency converting circuit (RC) 811 of the frequency converter 81 leads to the receiving circuit (R) 82 of the cordless telephone 8 converts the frequency f ₁₃ to f _11, thereafter the incoming call operation conventional cordless telephone Is exactly the same as
The control circuit (CNT) 84 detects the call signal and is visible,
If an audible signal is emitted and the subscriber responds, the call can be made with the caller.

Outgoing Call Operation from the cordless relay telephone 9 is exactly the same as the operation of the conventional cordless telephone, and therefore will not be described, and the call from the cordless telephone 8 will be described.

When the subscriber removes the transmission / reception circuit (TR) 85 from a hook (not shown), a hook switch (FS) 8
6 closes. Thus, the control circuit (CNT) 84 drives the transmission circuit (T) 83. Next, the transmission / reception circuit (T
If it is R) 85 from destination telephone number is dialed, from the transmitting circuit (T) 83, the dialing information is transmitted at the frequency f _12. The transmission frequency converter (T
C) 812, the outputs this to convert the radio frequency f _14.

[0009] In the cordless relay telephone 9, the receiving circuit (R) 99 detects the radio wave having the frequency f _{14, and} passes through a control circuit (CNT) 97, a hook switch (FS) 95, and a control circuit (CNT) 93. It drives the transmitter circuit (T) 92, thereby sending a radio wave of frequency f _12. The receiving circuit (R) 74 of the connecting device 7 receives this, arranges it into a switching center interface (not shown) by the control circuit (CNT) 72, and sends it to the telephone station via the subscriber line 6. If the called party (not shown) answers the call, the call is made in exactly the same manner as the conventional calling operation.

[0010]

In this conventional cordless telephone relay system, as shown in FIG. 2, the cordless relay telephone 9 is connected to the subscriber line 6 through the connection device 7, so that There is a problem that the cordless relay telephone 9 can be set only near the place where the subscriber line 6 exists. That is, when there is no cordless relay telephone 9, there is a problem that the cordless relay telephone 9 is installed only up to the position where the cordless telephone 8 is located at the position of the maximum effective distance from the terminal of the subscriber line 6.

[0011] Also, in this conventional example, since the cordless relay telephone 9 has a configuration in which transmission and reception is using only one set of frequency f _13, f _14, a plurality of cordless telephone 8
Therefore, there is a problem that it is not possible to reduce the traffic on the side of the exchange accommodating the subscriber's line 6 because the call cannot be relayed between the cordless telephones.

[0012]

SUMMARY OF THE INVENTION A cordless telephone relay system of the present invention relays transmission / reception of a call signal to / from a base station via a mobile radio communication network using a first set of frequencies having different frequencies for transmission / reception. The relay terminal device, and an effective distance between the relay terminal device and the relay terminal device, the plurality of second sets of frequencies having a smaller electric field strength than the first set of frequencies. A plurality of cordless telephones that communicate with each other via the base station, and wherein the relay terminal device transmits and receives signals at the first set of frequencies, and the plurality of cordless telephones. And second transmitting and receiving means for transmitting and receiving signals at the plurality of second sets of frequencies, and from the first set of frequencies to the second set of frequencies and from the plurality of second sets of frequencies to First
First conversion means for converting a frequency to a set of frequencies;
Second conversion means for performing mutual conversion between a third set of frequencies used by the calling party and a fourth set of frequencies used by the called party among the plurality of second sets of frequencies; Signal generating / transmitting means for generating a control signal including a busy signal and a busy release signal and transmitting the control signal using the second set of frequencies of the plurality of cordless telephones, and a terminal of each of the plurality of cordless telephones Storage means for storing a number and a use state; signal connection means for performing signal connection between the plurality of cordless telephones and the base station and signal connection between the cordless telephones during a call; First control means for controlling the entire system, wherein each of the plurality of cordless telephones generates a dial signal and transmits the dial signal to the relay terminal device at the third set of frequencies. A dial signal generator transmitting means, off-hook handset, a detection means for detecting the on-hook,
A third transmitting / receiving means for transmitting / receiving a signal to / from the relay terminal device using the third set of frequencies when detecting that no busy signal tone is generated at the time of calling; and detecting reception of the paging signal. Then, at the time of an incoming call, a fourth signal for transmitting / receiving a signal to / from the relay terminal device using the fourth set of frequencies is used.
And a second control means for controlling the entire inside of the cordless telephone.

A cordless telephone relay system according to the present invention comprises a relay terminal device for relaying transmission and reception of a call signal via a base station and a mobile radio communication network using first and second frequencies, and a relay terminal device. A third radio wave whose electric field strength is weaker than the first and second frequencies and whose effective distance is set in advance,
A plurality of cordless telephones that use the fourth, fifth, and sixth frequencies to communicate with the base station via the relay terminal device and that communicate with each other, wherein the relay terminal device is configured to transmit the first terminal from the base station to the first terminal; A first receiving circuit for receiving a signal at the frequency of the first, a first transmitting circuit for transmitting a signal at the second frequency to the base station, and the fourth or the sixth frequency received by the second A first frequency conversion circuit for converting to a frequency,
A second transmitting circuit for transmitting, at the third frequency, a signal to be transmitted from the plurality of cordless telephones and to a standby cordless telephone; and receiving a signal from the transmitted cordless telephone at the fourth frequency. A second receiving circuit, a third transmitting circuit for transmitting a signal to the cordless telephone of the plurality of cordless telephones to the incoming cordless telephone at the fifth frequency, and transmitting a signal from the incoming cordless telephone to the sixth telephone.
And a second receiving circuit for receiving the first and fourth frequencies and converting the first and fourth frequencies to the fifth frequency and for converting the first and sixth frequencies to the third frequency. A frequency conversion circuit, a storage circuit for storing a terminal number and a use state of each of the plurality of cordless telephones, a terminal number signal and a busy signal based on the storage of the circuit,
A signal generation circuit that generates a control signal including a call signal and a busy release signal; and a switching circuit that performs signal connection between the plurality of cordless telephones and the base station and connection of signals between the plurality of cordless telephones during a call. , A first control circuit for controlling the entire inside of the relay terminal device,
Each of the plurality of cordless telephones includes a telephone handset, a dial signal generation circuit that generates a dial signal, a signal tone generation circuit that generates a ringing tone and a busy signal tone, and an on-hook / off-hook of the handset. A hook switch for opening and closing, a fourth transmitting circuit for transmitting a signal at the fourth frequency when transmitting, a fourth receiving circuit for receiving a signal at the third frequency during transmitting, and a fifth receiving circuit for receiving a signal. A fifth receiving circuit for receiving a signal at the frequency of the second, a fifth transmitting circuit for transmitting a signal at the sixth frequency at the time of the incoming call, and a second transmitting circuit for controlling the whole inside of the cordless telephone.
Control circuit.

[0014]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In FIG. 1, a relay terminal device 1 for relaying transmission and reception of a call signal via a mobile radio communication network using frequencies f ₁ and f ₂ with a base station (not shown) and a relay terminal device 1 is set in advance and the frequency f _{3 of} the radio wave whose electric field strength is weaker than the frequencies f ₁ and f ₂ ,
f _4, f _5, the relay using f ₆ terminal cordless telephone 2a performs the base station and another call over a 1, 2
b, consists of a 2c, the relay terminal 1 transmitting circuit (T) 12a for transmitting and receiving circuit (R) 11a which receives the signal at frequency f ₁ from the base station, a signal at frequency f ₂ to the base station
When the cordless telephone 2a on the transmitting side, 2b, a frequency conversion circuit (CNV) 13 that converts the transmission frequency f ₄ or f ₆ of 2c to the frequency f ₂ of the transmission, a cordless telephone 2a,
2b, 2c and the T12c for transmitting T12b and frequency f ₅ signal to transmit the signal at frequency f _3, a cordless telephone 2a, 2b, which receives a signal 2c and the frequency f ₄ R1
And R11c to receive signals 1b and the frequency f _6, and CNV16 for converting a frequency f ₆ converts the frequency f ₄ to the frequency f ₅ to the frequency f _3, a busy signal to be sent to the cordless telephone set other than during a call, other than during a call A signal generation circuit (SG) 17 for generating a signal of each terminal number and a busy release signal of the cordless telephone and a calling signal for calling the cordless telephone, and mixing the signal generated by the SG 17 into a signal of a frequency during a call. Mixing circuit (M) 15a, 15b
A memory (MEM) 18 for storing the respective terminal numbers of the cordless telephones 2a, 2b, 2c and the respective states of the cordless telephones 2a, 2b, 2c, and signals of the cordless telephones 2a, 2b, 2c and the base station. A switching circuit (SW) 14 for connecting and connecting signals between the cordless telephones 2a, 2b, 2c, and a control circuit (CNT) for detecting an incoming / outgoing signal via R11a, R11b and controlling the MEM 18, BS17 and SW14. 19.

The cordless telephone 2a is a handset (TR)
29a, a dial signal generating circuit (DAL) 27a for generating a dial signal, a signal tone generating circuit (BSG) 26a for generating a ringing tone and a busy tone, and a hook switch (F) for opening and closing the TR 29a on and off hooks.
T for transmitting the S) 28a, a signal at a frequency f ₄ at the time of a transmission
22a and, R21 for receiving the signal at frequency f ₃ at the time of a transmission
and a, R23a to receive signals at a frequency f ₅ for incoming calls
When the T24a to transmit signals at a frequency f ₆ when receiving a call,
And a CNT 25a for controlling the entire cordless telephone 2a.

In the cordless telephones 2b and 2c, similarly to the cordless telephone 2a, R21b and 21c are respectively used.
, T22b and 22c, R23b and 23c, and T24
b, 24c, CNTs 25b, 25c, and BSG26
b, 26c, DAL 27b, 27c, FS28b,
28c and TRs 29b and 29c.

Next, the operation of this embodiment will be described.

When a call is made from a cordless telephone to a base station For example, when a call is made from a cordless telephone 2a to a device other than the cordless telephones 2b and 2c, the TR 29a is off-hook and a dial number "N" is transmitted from a DAL 27a. transmits a dial signal "N" by the frequency f ₄ when originating from R21a. When the relay terminal device 1 receives the dial signal “N” at the frequency f ₄ by R11b, the CNT 19 determines that the transmission is to the base station via the MEM 18 and sets R11b and T12b to T
SW 14 to be connected to 12a and R11a is controlled.

[0021] Also, CNT19 sends a busy signal by the frequency f ₃ from T12b is mixed with a cordless phone 2b controls the SG17, by generating a terminal number and a busy signal 2c M15a.

CNTs 25b, 25c of cordless telephones 2b, 2c receiving busy signals at R21b, R21c
Receives the terminal number and the busy signal, and
G26b and 26c are activated. TR29b or 29c
If the user goes off-hook, a busy sound is heard through the FSs 28b and 28c.

In the relay terminal device 1, the dial signal “N” of the frequency f ₄ via the SW 14 is transmitted to the CNV 13 by the frequency f
₂ is converted to a dial signal “N”. The response signal of the frequency f ₁ from the base station to the dial signal “N” is R
Received at 11a, cordless telephone 2a from T12b is converted to a frequency f ₃ in CNV16 via SW14
Sent to

When the cordless telephone 2a is connected to the base station via the relay terminal device 1 in this way, the transmission / reception signal from the cordless telephone 2a is transmitted and received at frequencies f ₄ and f ₃ , and these frequencies f ₄ , F ₃ are relay terminal devices 1
Are converted to frequencies f ₂ and f ₁ , and the call is made to the other party's telephone via the base station.

In the case of a call between cordless telephones accommodated in the relay terminal device 1, for example, when a call is made by calling from the cordless telephone 2a to the cordless telephone 2b, as in the case described above, after the TR 29a is taken off-hook, D
When calling the dial number "M" of the cordless telephone 2b from AL27a, CNT25a is transmitting a dial signal "M" by the frequency f ₄ when originating from R21a.

When the relay terminal device 1 receives the dial "M" at the frequency f4 by R11b, the CNT 19 switches R11b and T12b to T through the MEM 18 to connect to the cordless telephone 2b accommodated in the relay terminal device 1.
SW14 is controlled so as to be connected to 12c and R11c.

[0027] Also, CNT19 both transmits a busy signal by the frequency f ₃ from T12b is mixed M15a by generating a terminal number and the busy signal of the cordless telephone 2c controls the SG17, cordless phone and controls the SG17 2b to generate a terminal number and a call signal
Mixed to 15b transmits the call signal by the frequency f ₅ from T12c with.

Since the busy signal is the same as that in the above-mentioned operation, the description is omitted.

The calling signal is R33 of the cordless telephone 2b.
b, the CNT 25b activates the BSG 26b and makes it sound in response to receiving its own terminal number. When the CNT 25b detects that the TR 29b goes off-hook via the FS 28b, the sound of the BSG 26b is stopped.

Since the cordless telephone 2b is the receiving side, the transmission / reception signal from the TR 29b is T24b, R23b
Are transmitted and received at frequencies f ₆ and f ₅ .

In the relay terminal device 1, the cordless telephone 2a
Handset signals from T12b, are transmitted and received at a frequency f _4, f ₃ by R11b, also handset signals from the cordless telephone. 2b T12C, frequency by R11c f
₆ and f ₅ , and the frequency f ₄
Is converted to a frequency f ₅ , and the frequency f ₆ is converted to a frequency f ₃ , and the transmission and reception signals are mutually connected by the SW 14 under the control of the CNT 19.

In the case of an incoming call from the base station to the cordless telephone accommodated in the relay terminal device 1, the relay terminal device 1
a, when a call signal from the base station is detected via the SW 14, the terminal number in the call signal is stored in the MEM 18 and the result of the reference, for example, the accommodated cordless telephone 2a
When consistent with the number and the terminal number of the calling signal and the cordless telephone 2a Start SG17 by mixing with M15b, so for incoming, is transmitted at a frequency f ₅ from T12C.

In the cordless telephone 2a, the CNT 25a has an R
When the own terminal number is detected in the calling signal received via 23a, the BSG 26a is activated and a ringing tone sounds. TR
When 29a goes off-hook, CNT 25a becomes BSG2
The sound is stopped for 6a. Cordless telephone 2a
Is the receiving side, the transmission / reception signal from the TR 29a is T
23a, it is transmitted and received by the frequency f _6, f ₅ by R24a.

In the relay terminal device 1, the cordless telephone 2a
Handset signals from T12C, transmit and receive at the frequency f _6, f ₅ by R11c, received signals received by the R11c is transmitted from T12a converted to a frequency f ₂ in CNV13 via SW14 to the base station, the base station From the frequency f ₁
In the received signal received by R11a is via SW14, is transmitted from T12c are converted into a frequency f ₅ in CNV16 to the cordless telephone 2a.

In the case of an incoming call of the cordless telephone 2a, the CNT 19 is set to SG1 similarly to the above two cases.
7 is started, the terminal numbers of the cordless telephones 2b, 2c and the busy signal are generated and mixed by M15a, and
b from the feed the busy signal at the frequency f ₃ R21b, R21
CNTs 25b and 25c received by BSG are BSGs 26b and 2
6c is activated to generate a busy sound. TR29b, 2
When 9c goes off-hook, this busy sound becomes TR29b,
Listening at 29c, it knows that the wireless communication line to the base station is busy.

The cordless telephone 2a ends the call, and TR29
When "a" is on-hook, the CNT 25a detects the on-hook via the FS 28a, and sends an end signal to the relay terminal device 1 through T24a.

When the relay terminal device 1 detects the end signal through R11c, it sends the end signal to the base station through T12a, activates SG17, and sends the terminal to the cordless telephones 2b and 2c that have been sending the busy signal. the number and busy state signal is mixed with M15a transmits at frequency f ₃ through T12b with.

In the cordless telephones 2b and 2c, when each of the CNTs 25b and 25c receives its own terminal number and busy release signal through R21b and 21c, the BSG
26b and 26c are activated to stop the generation of the busy signal sound.

When the relay terminal apparatus 1 detects the end signal from the base station through the R11a by the CNT 19,
A call end signal is transmitted to the cordless telephone 2a through T12c, and a busy release signal is transmitted to the cordless telephones 2b and 2c through T through b in the same procedure as described above.

The method of releasing the busy in the above two operations is performed in the same procedure as described above.

As described in this embodiment, the three cordless telephones 2a, 2b, and 2c use frequencies f ₁ and f ₂ common to the three telephones when talking to the base station. In the case of two-way communication, the effective distances between the relay terminal device 1 and the cordless telephones 2a, 2b, 2c are set using the radio wave frequencies f ₃ , f ₄ , f ₅ , f ₆ for which a preset distance has been set. Therefore, there is an effect that a limited number of frequencies used in the base station can be effectively used and traffic at the base station can be reduced more than before.

Also, since the relay terminal device 1 can be installed in a place without a wired telephone line, the cordless telephones 2a, 2
There is an effect that b and 2c can be used in a wide range.

[0043]

As described above, the present invention relates to a relay terminal device for relaying transmission / reception of a call signal to / from a base station via a mobile radio communication network using a first set of frequencies having different frequencies in transmission / reception. And a base station via the relay terminal using a plurality of second sets of frequencies whose effective distances to the relay terminal are set in advance and the electric field strength of which is weaker than the first set of frequencies. With a configuration including a plurality of cordless telephones that communicate with each other, the frequencies directly used when the plurality of cordless telephones communicate with each other belong to the first set of frequencies used in the mobile radio communication network. Since the group frequencies are not used, there is an effect that the limited frequencies of these groups can be effectively used.

In the case of a mutual call between a plurality of cordless telephones, the call is performed using the second set of frequencies.
There is an effect that traffic on the base station side can be reduced more than before.

Further, since the relay terminal device is not connected to a wired telephone line, it can be installed even in a place without a telephone line, so that a plurality of cordless telephones can be used in a wide range.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Relay terminal apparatus 2a, 2b, 2c Cordless telephone 11a, 11b, 11c Receiving circuit (R) 12a, 12b, 12c Transmitting circuit (T) 13, 16 Frequency conversion circuit (CNV) 14 Switching circuit (SW) 15a, 15b Mixing Circuit (M) 17 Signal generation circuit (SG) 18 Memory (MEM) 19 Control circuit (CNT) 21a, 21b, 21c Receiving circuit (R) 22a, 22b, 22c Transmitting circuit (T) 23a, 23b, 23c Receiving circuit ( R) 24a, 24b, 24c Transmission circuit (T) 25a, 25b, 25c Control circuit (CNT) 26a, 26b, 26c Signal tone generation circuit (BSG) 27a, 27b, 27c Dial signal generation circuit (D
AL) 28a, 28b, 28c Hook switch (FS) 29a, 29b, 29c Handset (TR)

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-336030 (JP, A) JP-A-61-72422 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04B 7/24-7/26 102 H04Q 7/00-7/38

Claims (3)

(57) [Claims] 1. A relay terminal device for relaying transmission / reception of a call signal to / from a base station via a mobile radio communication network using a first set of frequencies having different frequencies for transmission / reception, and an effective communication between the relay terminal device and the relay terminal device. A call is established between the base station and the base station via the relay terminal device using a plurality of second sets of frequencies whose distances are set in advance and the electric field strength of which is weaker than the first set of frequencies. A plurality of cordless telephones, wherein the relay terminal device transmits and receives signals at the first set of frequencies, and transmits signals at the plurality of cordless telephones and the plurality of second sets of frequencies. A second transmitting / receiving means for transmitting / receiving, the second set of frequencies from the first set of frequencies;
First conversion means for converting the frequency to the set of frequencies and from the second set of frequencies to the first set of frequencies, and the transmitting side of the plurality of second sets of frequencies comprises: Second conversion means for performing mutual conversion between the third set of frequencies used and the fourth set of frequencies used by the terminating side; and generating a control signal including a call signal, a busy signal and a busy release signal. Signal generation / transmission means for transmitting using the second set of frequencies of the plurality of cordless telephones, storage means for storing terminal numbers and use states of the plurality of cordless telephones, Signal connection means for connecting signals between a plurality of cordless telephones and the base station and signal connection between the cordless telephones, and first control means for controlling the entire inside of the relay terminal device; Duplicate Each of the number of cordless telephones includes a dial signal generating and transmitting means for generating a dial signal and transmitting the dial signal to the relay terminal device at the third set of frequencies; a detecting means for detecting off-hook and on-hook of the handset; A third transmitting / receiving means for transmitting / receiving a signal to / from the relay terminal device using the third set of frequencies when detecting that no busy signal tone is generated, and detecting reception of the paging signal. A fourth transmission / reception unit for transmitting / receiving a signal to / from the relay terminal device using the fourth set of frequencies when receiving a call; and a second control unit for controlling the entire inside of the cordless telephone. A cordless telephone relay system. 2. A relay terminal device for relaying transmission / reception of a call signal via a base station and a mobile radio communication network using first and second frequencies, and an effective distance between the relay terminal device and the relay terminal device are set in advance. And using the third, fourth, fifth, and sixth frequencies of radio waves whose electric field strength is weaker than the first and second frequencies, to communicate with the base station and the base station via the relay terminal device. A plurality of cordless telephones, wherein the relay terminal device receives a signal at the first frequency from the base station, and transmits a signal at the second frequency to the base station. 1 transmission circuit, a first frequency conversion circuit for converting the received fourth or sixth frequency to the second frequency, and a signal to be transmitted from the plurality of cordless telephones and to a standby cordless telephone. At the third frequency A second receiving circuit for receiving a signal from the outgoing cordless telephone at the fourth frequency; and transmitting a signal to the incoming cordless telephone of the plurality of cordless telephones to the fifth frequency. A third transmitting circuit for transmitting a signal from the incoming cordless telephone at the sixth frequency.
And a receiving circuit for converting the first and fourth frequencies to the fifth frequency and converting the first and sixth frequencies to the third frequency.
A second frequency conversion circuit for converting the terminal number of each of the plurality of cordless telephones, a storage circuit for storing a terminal number and a use state of each of the plurality of cordless telephones, a terminal number signal, a busy signal, and a call signal based on the storage of the circuit. A signal generation circuit that generates a control signal including a signal and a busy release signal, and a switching circuit that performs connection of signals between the plurality of cordless telephones and the base station and connection of signals between the plurality of cordless telephones during a call, A first control circuit for controlling the entire inside of the relay terminal device. 3. Each of the plurality of cordless telephones includes a telephone handset, a dial signal generation circuit for generating a dial signal, a signal tone generation circuit for generating a ringing tone and a busy tone, and the handset. A hook switch that opens and closes on and off hooks, and the fourth
A fourth transmitting circuit for transmitting a signal at the frequency of the second, a fourth receiving circuit for receiving the signal at the third frequency at the time of transmission, and a fifth receiving circuit for receiving a signal at the fifth frequency at the time of incoming call 3. The cordless telephone according to claim 1, further comprising a circuit, a fifth transmitting circuit for transmitting a signal at a sixth frequency when the incoming call is received, and a second control circuit for controlling the entire inside of the cordless telephone. Cordless telephone relay system.