JPH01136437A - Cordless telephone set - Google Patents

Abstract

PURPOSE:To attain communication between mobile stations by using an extension identification number so as to identify each slave respectively. CONSTITUTION:A master station 3 uses a control channel 6 to designate one of plural communication channels 7 and a 2-way radio line is constituted with a slave station 4 or 5. When the slave station 4 calls the slave station 5, a control section of the slave station 4 detects an idle communication channel to set the transmission frequency to the outgoing frequency 400MHz of the control channel and the reception frequency to the incoming frequency 250MHz of the control channel respectively. Thus, the 2-way communication by the control channel is attained between the slave stations 4 and 5. Then an extension call signal 110 is sent to slave station 5 to designate the communication channel. Thus, two sets of slave stations are used for one set of the master station.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cordless telephone device, and in particular, to a cordless telephone device that has a plurality of mobile stations for one fixed station and that allows telephone calls to be made between the mobile stations. The present invention relates to a cordless telephone device that can be used as a telephone.

[Conventional technology]

Since wireless communication does not require communication lines, it is an effective means of communication suitable for mobile bodies, and is used in various mobile communications such as automatic telephones and ship telephones.

Cordless telephone equipment is one of the wireless telephone systems that utilizes this feature of freedom of movement.

Cordless telephone equipment places a fixed station (hereinafter referred to as a master station) at the terminal of a public line connected to an exchange, and uses low-output radio waves to communicate with a mobile station (hereinafter referred to as a slave station). It constitutes a four-wire two-way radio line between the two terminals, and its use has recently become popular in various fields due to the convenience of being able to freely carry the handset (i.e., slave station) anywhere within the range of the radio waves. It is rapidly expanding.

Conventionally, in order to avoid mixing with other cordless telephone devices that are used in close proximity, cordless telephone devices are assigned a specific frequency, and each cordless telephone device that uses the same frequency is distinguished by a tone signal. However, with this method, frequency utilization is poor, and as the number of uses increases, it is difficult to prevent interference, and erroneous billing (for example, when a call is made from a slave station of a certain cordless telephone device) This may cause a call that is connected to another cordless telephone device to be connected through the master station due to interference, and the telephone charges in that case will be erroneously billed as the telephone charges for the other cordless telephone device. This is one of the factors hindering expansion.

Therefore, as a means to solve this problem, a multi-channel access system is attracting attention in which a single control channel and a plurality of call channels are commonly used by a plurality of cordless telephone devices.

This multi-channel access method is a line connection method that is also used in car telephone systems, etc. When a call occurs, a calling or incoming call signal (a digitally encoded identification number of each cordless telephone device) is used. (including) or a response thereto, and specifying the communication channel to be used.1. A control channel is used to transmit calls and other signals (for example, dialing signals, end-of-call signals, etc.) using a designated call channel.

Regarding cordless telephone devices using this multi-channel access method, for example, Japanese Patent Laid-Open No. 6
No. 0-128, Japanese Patent Application Laid-Open No. 60-204134,
JP-A No. 61-52037 and the like can be mentioned.

[Problem that the invention seeks to solve]

The above conventional technology takes into account only the case where one slave station is used as a pair for one master station, and does not consider the case where multiple slave stations are used for one master station. There wasn't.

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide a cordless telephone device in which a plurality of slave stations can be used for one master station. A second object of the present invention is to provide a cordless telephone device that allows telephone calls to be made between a plurality of slave stations.

[Means for solving problems]

In order to achieve the first of the above objectives, the present invention provides a plurality of slave stations, each assigned a different extension identification number, and a master station that uses a control channel. Specify one of multiple call channels,
Among the plurality of slave stations, it is possible to wirelessly connect to at least one slave station.

In addition, in order to achieve the second object, the present invention provides each of the plurality of slave stations with switching means for switching the passbands of the bandpass filters of the transmitting section and the receiving section, and for transmitting and transmitting a signal at a specified frequency. A frequency setting means for receiving, an empty channel detecting means for detecting an empty communication channel from a plurality of communication channels, and an extension/external line switching means for switching between an extension and an outside line are provided.

[Effect]

In the present invention, even if there are a plurality of slave stations, each slave station can be identified by using the extension identification number.

Therefore, for example, when making an outside call, when a slave station calls the master station using its own extension identification number, the master station can identify which slave station is making the call from the extension identification number. Then, by specifying one of the plurality of call channels for the slave station using the control channel and establishing a wireless connection with the slave station, the slave station makes an outside line call via the master station. be able to.

In addition, in the case of an incoming external call, the master station calls all the slave stations using the extension identification number, specifies one of the plurality of call channels for each slave station using the control channel, and calls each slave station. By establishing a wireless connection with a slave station, you can go off-hook from any slave station and make an outside line call.

Further, in the present invention, when a certain first slave station among the plurality of slave stations switches the extension/external line switching means to the extension side to call a certain second slave station, the vacant channel detection The means detects an empty communication channel from a plurality of communication channels, and then the frequency setting means changes the transmission frequency of the first slave station to the reception frequency of the control channel in the second slave station. The reception frequency of the first slave station is set to the transmission frequency of the control channel in the second slave station, the pass band of the bandpass filter is also switched accordingly by the switching means, and the second slave station The detected communication channel is specified to the slave station using the control channel. By doing so, it is possible to perform an extension call between the first slave station and the second slave station using the specified call channel.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is an explanatory diagram schematically showing the overall configuration of a cordless telephone device as an embodiment of the present invention.

In Fig. 2, 1 is an exchange, 2 is a public line, 3 is a fixed station (hereinafter referred to as the master station), 4 is a mobile station (hereinafter referred to as slave station), and 5 is a mobile station ( Hereinafter referred to as slave station ■.)
It is.

As shown in FIG. 2, the master station 3 is connected to the exchange 1 via the public line 2. As shown in FIG. In addition, the master station 3 specifies one of the plurality of call channels 7 using the control channel 6, and configures a bidirectional wireless line with the slave station ■; 4 or slave station ■: 5. do.

For both channel 6 and communication channel 7, the direction from the master station to the slave station is called the downlink, and the frequency of the line in that direction is called the downlink frequency. The direction from the slave station to the master station is called uplink, and the frequency of the line in that direction is called uplink frequency. , Here, the down frequency of the control channel 6 is 400 MHz, and the up frequency is 250 MHz.

Next, the configurations of the master station and slave stations (2) and (2) in FIG. 2 will be explained in detail.

FIG. 1(a) is a block diagram showing the detailed configuration of the master station in FIG. 2, FIG. 1(b) is a block diagram showing the detailed configuration of the slave station ■ in FIG. ) is a block diagram showing the detailed configuration of slave station (2) in FIG. 2.

In FIG. 1(a), 1o is a line relay circuit for connecting and opening the public line 2, 11 is an incoming call detection circuit for detecting a ringing signal from exchange 1, and 12 is a hybrid for 2-wire and 4-wire switching. circuit, 13.14 is an amplifier, 15.
16 is a mute circuit for turning on the amplifiers 13 and 14, 17 is a transmitting section with a channel switching function, 18 is a receiving section with a channel switching function, 19.20
is a frequency synthesizer for switching channels, 2
1. 22 is a bandpass filter, 23 is a data transmission section, 24 is a data detection section, 25 is an empty channel detection circuit for detecting an empty communication channel among a plurality of communication channels, and 26 is a detection circuit for detecting interference in communication channels. 27 is an antenna, 28 is a dial circuit for sending a dial signal or a button signal to the exchange 1, and 29 is a control unit for controlling the operation of the master station.

In addition, in FIGS. 1(b) and (c), 30.31 is an antenna, 32, 33, 38.39 is a bandpass filter, and 34.
35 is a transmitter having a channel switching function, 36.37.
42.43 is an amplifier, 40°41 is a receiving section with a channel switching function, 44°45 is a data sending section, 46.47
is a data detection unit, 48, 49, 50; 51 is a frequency synthesizer for switching channels, 52, 53
, 54° 55 turns amplifiers 36, 37, 42, 43 ON1
56.57 is an empty channel detection circuit that detects an empty communication channel among a plurality of communication channels; 58.59 is an interference detection circuit that detects interference between communication channels; 60.61, 62 ．．
63 is a switching circuit for switching the passband of the bandpass filter 32, 33, 38, 39, 64.65 is a hook switch, 66
．． 67 is an extension line/external line switch that switches between internal and external lines;
68, 69 are dial keys, 70.71 is a transmitter, 72
73 is a receiver, 74.75 is a control unit that controls the operation of the slave station, and 76.77 is a ringer circuit that rings a bell.

Next, the operation of one embodiment of the present invention will be explained.

(1) Making an outside line FIG. 3 shows the sequence of the outside line calling operation.

When on standby, the master station 3. Child station ■: 4. Both slave stations ■ and 5 are waiting to receive the control channel. In other words, Figure 1 (
The transmission frequency of the master station 3 shown in a) is the frequency synthesizer 1.
Control channel downlink frequency (400MHz) by 9
The receiving frequency is set to Frequency Synthesizer 2.
0 indicates the upstream frequency of the control channel (250MHz)
is set to . On the other hand, the slave station ■ shown in FIGS. 1(b) and (C); 4. On the contrary, in slave station ①;5, the transmission frequency is set to the upstream frequency of the control channel (250 MHz), and the receiving frequency is set to the downstream frequency of the control channel (400 MHz).

Now, when the slave station ■; 4 shown in FIG. A calling signal 80 is transmitted as shown in FIG.

The structure of the calling signal 80 is shown in FIG.

In FIG. 6, 120 is a preamble (PRE), 1
21 is a frame synchronization signal (FS), 123 is a control signal type (C3), 124 is a self address (SA), 125 is a partner address (DA), and 126 is a device identification signal (ID).
, is.

Here, the address is an identification number for identifying each station, and is the same as an extension number. That is, the address of the slave station ■ is "1", the address of the slave station ■ is "2", and the address of the master station is "0". The device identification signal is an identification code for identifying this cordless telephone device from other cordless telephone devices, and is therefore common to the master station, slave station (2), and slave station (2).

In the above case, the slave station ■;4 sends a calling signal 8 to the master station 3.
0, the self address 124 shown in FIG. as an identification signal of this cordless telephone device.

Next, the calling signal 80 transmitted from the slave station 4 using the control channel is received by the master station 3 and the slave station 5, respectively. The master station 3 and the slave station 1;
24 is detected to determine from which station the calling signal was sent, and the other party's address 125 and device identification signal 126 are detected to determine whether the calling signal is addressed to the local station. Identify whether the signal is coming or not.

For example, in the data detection unit 24 of the master station 3, since the self address 124 is "1" indicating the address of the slave station ■, this calling signal 80 is a signal sent from the slave station ■;4. Furthermore, since the destination address 125 is "O" indicating the address of the own station, and the device identification signal 126 is the same identification signal as the own station, this calling signal is a signal addressed to the own station. .

Therefore, the master station 3 detects an empty communication channel from among the plurality of communication channels using the empty channel detection circuit 25 shown in FIG. , via the control channel by the call response signal 81 shown in FIG. 3, and the frequency synthesizer 19.20 shown in FIG. is set to that upstream frequency.

On the other hand, the slave station ■;4 which has received the designated communication channel uses the frequency synthesizer 48.50 shown in FIG. Set to .

As a result, a bidirectional communication channel is formed between the master station 3 and the slave station 4;

A slave station that has completed switching to the specified call channel■;
4 uses the communication channel to transmit a channel switching completion signal 82 to the master station 3 as shown in FIG.
After confirming that it is an empty channel by the interference detection circuit 58 shown in b), an interference wave detection completion signal 83 is transmitted to the master station 3 as shown in FIG.

The master station 3 closes the line relay circuit 10 shown in FIG. 1(a), captures the line, and sends an amplifier ON signal 84 shown in FIG. 3 to the slave station 4 to turn on the amplifier.
Instruct by. In response to this, the control section 74 of the slave station ■;4 shown in FIG. 1(b) cancels the mute circuit 52.54 and turns on the amplifier 36.42.

The user receives the dial tone 8 shown in FIG. 3 from the exchange 1.
5, press the dial key 68 shown in FIG. 1(b).
Enter your phone number using . Then, the control unit 74 of the slave station ■:4 transmits a dial signal 86 to the master station 3 as shown in FIG. When the master station 3 receives the dial signal 86, the dial circuit 28 shown in FIG. 1(a) transmits a dial pulse or push button (PB) signal 82 to the exchange 1 as shown in FIG. , and then an outside line call 88 is made.

When the call 88 ends and the slave station ■;4 is on-hook,
The control unit 74 of the slave station 4 shown in FIG. 1(b) controls the master station 3.
In response, it transmits an on-footer signal 89 and a call-end signal 90 as shown in FIG. 3, and returns to the standby state. The master station 3 opens the line relay circuit 10 shown in FIG. 1(a) and returns to the standby state.

(2) Incoming external call FIG. 4 shows the sequence of an outside call receiving operation.

As shown in FIG. 4, calling signals 95 from exchanges 1 to 167
is sent, the control unit 29 of the master station 3 shown in FIG. 1(a) detects this with the incoming call detection circuit 11, and transmits the control channel to all slave stations as shown in FIG. The incoming call signal 96 is transmitted all at once.

, the structure of the incoming call signal 96 is shown in FIG.

In FIG. 7, 127 is a preamble (PRE), 1
28 is a frame synchronization signal (FS), 129 is the channel number (CH) of the designated communication channel, 130 is the own address (SA), 131 is the other party's address (DA), 1
32 is a device identification signal (ID).

In the above case, the master station 3 sends an incoming call signal 9 to all slave stations.
6, the self address 130 shown in FIG.
represents a hexadecimal number. ), and transmits the device identification signal 132 as the identification signal of the cordless telephone device.

Next, the incoming call signal 96 transmitted from the master station 3 using the control channel is received by the slave station ①; 4 and slave station ①: 5, respectively. The slave station ■; 4 and the slave station ■; 5 each detect the own address 130 of the incoming call signal 96 in their respective data detection units 46 and 47, and detect the own address 130 of the incoming call signal 96.
is rQJ indicating the address of the master station 3, the incoming call signal 96 is identified as a signal sent from the master station 3, and the other party's address 131 and device identification signal 132 are detected. r where the destination address 131 indicates simultaneous notification
Since it is FFHJ and the device identification signal 126 is the same identification signal as the own station, this calling signal is identified as a signal addressed to the own station.

Therefore, slave station ■;4 and slave station ■;5 are respectively the fourth
As shown in the figure, the incoming call response signal 9 is transmitted using the control channel.
After returning 7.98 to the master station 3, each frequency synthesizer switches from the control channel to the designated communication channel, and transmits a channel switching completion signal 99,100 to the master station 3 using the communication channel, Furthermore, after confirming that it is an empty channel, interference wave detection completion signals 101 and 102 are transmitted to the master station 3. and,
The master station 3 transmits a bell ringing signal 103 to all the slave stations, and the slave stations ■; 4 and ■; 5 receive the bell ringing signal 103, and the slave stations ■; -Circuit 76.77
Sends out a ring tone.

Now, suppose slave station ■;5 goes off-hook, as shown in Figure 1 (c
) The transmitting unit 35 of the slave station ■;5 shown in FIG. Slave station ■ that received the off-footer signal 104;
4 stops sending out the ringing tone and returns to the standby state.

On the other hand, the master station 3 that has received the off-hook signal 104 causes the line relay circuit 10 to capture the ONL line, and instructs the slave station 5 to turn on the amplifier using the amplifier ON signal 105 shown in FIG. , a call 106 is made. The subsequent operations are performed in the same manner as in the case of making an outside line call.

(3) Extension call FIG. 5 shows a sequence of extension call operations.

When calling slave station ■; 5 from slave station ■; 4, the user presses the extension/external line selector switch 6 of slave station ■;
After switching 6 to the extension side, by operating the dial key 68, the slave station ■;5 is selected.

The control unit 74 of the slave station ■; 4 controls the idle channel detection circuit 5
6 detects an empty communication channel from among a plurality of communication channels, and then the transmission frequency is set to the downlink frequency of the control channel (40
The frequency synthesizer 50 sets the reception frequency to the upstream frequency (250MHz) of the control channel, and the switching circuits 60 and 62 change the passband of the transmitting side bandpass filter 32 to the upstream frequency band (250MHz).
0 MHz band), and the passband of the bandpass filter 38 on the receiving side is switched to the downlink frequency band (400 MHz band).

As a result, two-way communication via the control channel becomes possible between the slave station (2);4 and the slave station (2);5.

Next, the control unit 74 of the slave station ■;4 shown in FIG. 1(b)
From the data transmitter 44, the slave station ■
; 5, an extension calling signal 110 is transmitted as shown in FIG. 5, and a call channel is designated.

After receiving this, the control unit 75 of the slave station ■;5 shown in FIG. 1(c) returns a paging response signal 111 to the slave station ■;4 using the control channel as shown in FIG. , 1st
By the frequency synthesizer 49.51 shown in figure (c),
The transmission frequency is set to the upstream frequency of the specified communication channel, and the reception frequency is set to the downstream frequency of the specified communication channel.

On the other hand, the slave station ■;4 which received the paging response signal 111,
Frequency synthesizers 48 and 50 shown in FIG. 1(b) each set the transmission frequency to the downlink frequency of the specified communication channel and the reception frequency to the uplink frequency of the specified communication channel.

As a result, a bidirectional communication channel is formed between the slave station (2);4 and the slave station (2):5.

A slave station that has completed switching to the specified call channel■;
5 uses the call channel to send the 5th call to the slave station ■; 4.
As shown in the figure, a channel switching completion signal 112 is transmitted,
After confirming that it is an empty channel by the interference detection circuit 59 shown in FIG. 1(c), it transmits an interference wave detection completion signal 113 to the slave station 4; as shown in FIG. The slave station ■;4 that received this sends the bell ringing signal 1 as shown in Figure 5.
14 is transmitted to the slave station (2);5, which receives it and sends out a ringing tone through the ringer circuit 77 shown in FIG. 1(C).

When the slave station ■;5 is off-hook, the transmitter 35 of the slave station ■;5 shown in FIG. 1(C) transmits an off-footer signal 115 to the slave station ■;4 as shown in FIG. The slave station ■; 4 that received this transmits the mute circuit 52.4 shown in FIG. 1(b).
54 and turn on the amplifiers 36 and 42,
As shown in Figure 5, amplifier ON signal 11 for slave station ■;
Send 6. In response, the slave station ■;5 receives the request and sends the
), the mute circuits 53 and 55 shown in FIG.
As shown in FIG. 5, a telephone call 117 is made with the slave station (2);4.

When the call 117 ends and the slave station ■; 5 is on-hook, the control unit 75 of the slave station ■; 5 shown in FIG. 1(c) controls the slave station ■; 4 as shown in FIG. 5. on footer signal 118
Then, it transmits a call end signal 119 and returns to the standby state. In response to this, the slave station 4 uses the frequency synthesizer 48.50 shown in FIG. By circuit 60.62,
The passband of the bandpass filter 32 on the transmitting side is switched to the upstream frequency band of the control channel, and the passband of the bandpass filter 38 on the receiving side is switched to the downlink frequency band of the control channel, and the process returns to the standby state.

As described above, according to this embodiment, two slave stations can be used for one master station, and furthermore, telephone calls can be made between the slave stations. Furthermore, when making a call between slave stations, only one communication channel is used, so there is an effect that the use efficiency of the communication channel is high.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to use a plurality of slave stations for one master station, and moreover, it is possible to make calls between the plurality of slave stations. .

Furthermore, when making a call between slave stations, only one communication channel is used, so there is an effect that the efficiency of use of the communication channel is high.

Furthermore, when making a call between slave stations, the master station is not involved, so for example, even if there are three slave stations and one slave station is making an outside line call via the master station, Extension calls can be made simultaneously between the remaining two slave stations.

[Brief explanation of the drawing]

FIG. 1(a) is a block diagram showing the configuration of the master station in one embodiment of the present invention, FIG. 1(b) is a block diagram showing the configuration of the slave station FIG. 2 is an explanatory diagram schematically showing the overall configuration of an embodiment of the present invention; FIG. 3 is an explanatory diagram showing the sequence of an outside line originating operation in an embodiment of the present invention. Figure 4 is an explanatory diagram showing the sequence of the outside call receiving operation, and Figure 5 is
6 is an explanatory diagram showing the sequence of the extension call operation, FIG. 6 is an explanatory diagram showing the structure of the calling signal in FIG. 3, and FIG. 7 is an explanatory diagram showing the structure of the incoming call signal in FIG. 4. be. Explanation of symbols 2...Public line, 3...Main station, 4...
...Slave station ■, 5...Slave station ■, 21, 22.
32, 33, 38° 39...Band filter, 17
．． 34.35... Transmission section, 18.40.41.
...Receiving section, 23.44°45...Data sending section, 24,46.47...Data detection section,
25.56.57...Empty channel detection circuit, 66.67...Extension/external line selection switch, 19
．． 20.48, 49, 50.51... Frequency synthesizer, 29.74.75... Control unit, 6
0.61, 62.63...Switching circuit. Agent Patent Attorney Akio NamikiFigure 3Figure 5Figure 6

Claims (1)

[Claims] 1. Consisting of a fixed station connected to a public line and a mobile station that can be wirelessly connected to the fixed station, the fixed station configures a bidirectional wireless line with the mobile station. In the cordless telephone device, the mobile station is composed of a plurality of mobile stations, each of which is assigned a different extension identification number, and the fixed station specifies one of the plurality of call channels using a control channel, and A cordless telephone device characterized in that it is capable of wirelessly connecting to at least one mobile station among the mobile stations. 2. In the cordless telephone device according to claim 1, a first mobile station among the plurality of mobile stations that wants to make an outside line call uses the control channel to send the call to the fixed station. transmitting a calling signal including the extension identification number of the first mobile station, the fixed station searches for an empty call channel, and sends a calling signal including the empty call channel information and the extension identification number of the first mobile station. The first mobile station transmits a call response signal using the control channel, and the first mobile station communicates with the public via the fixed station by using the communication channel specified by the free communication channel information of the call response signal. A cordless telephone device characterized by being connected to a line. 3. In the cordless telephone device according to claim 1, when a call occurs from the public line, the fixed station searches for an empty call channel and sends an incoming call signal containing information on the empty call channel. By simultaneously transmitting to the plurality of mobile stations using the control channel, each of the plurality of mobile stations transmits a ringing tone, and among them, a certain second mobile station that goes off-hook earliest , After transmitting off-hook signals all at once using a communication channel specified by the control channel or the free communication channel information of the incoming call signal, the off-hook signal is transmitted via the fixed station by using the specified communication channel. 1. A cordless telephone device connected to a public telephone line, wherein other mobile stations return to a standby state upon receiving the off-hook signal. 4. Consisting of a fixed station connected to a public line and a plurality of mobile stations wirelessly connected to the fixed station, the fixed station specifies one of the plurality of communication channels using a control channel, In a cordless telephone device capable of configuring a bidirectional wireless line with at least one of the plurality of mobile stations, each of the plurality of mobile stations is provided with a bandpass filter of a transmitting section. a first switching means for switching the passband of the bandpass filter of the receiving section, a second switching means for switching the passband of the bandpass filter of the receiving section, and a transmission frequency setting means for transmitting the signal at a specified frequency;
A reception frequency setting means for receiving a signal of a specified frequency, an empty channel detection means for detecting an empty communication channel from the plurality of communication channels, and an extension/external line switching means for switching between an internal line and an external line are provided. , when a certain first mobile station among the plurality of mobile stations switches the extension/external line switching means to the extension side to call a certain second mobile station, the vacant channel detection means A vacant communication channel is detected from the communication channels, and the transmission frequency setting means sets the transmission frequency of the first mobile station to the reception frequency of the control channel of the second mobile station (hereinafter referred to as the first frequency). ), the first switching means switches the passband of the bandpass filter of the transmitter to a first frequency band including the first frequency, and the reception frequency setting means switches the passband of the bandpass filter of the transmitter to a first frequency band including the first frequency.
The reception frequency of the mobile station is set to the transmission frequency of the control channel in the second mobile station (hereinafter referred to as the second frequency), and the second switching means sets the reception frequency of the bandpass filter of the reception section. Switching the passband to a second frequency band including the second frequency, specifying the detected communication channel to the second mobile station using the control channel, and then changing the transmission frequency. The setting means sets the transmission frequency of the first mobile station to the reception frequency of the designated communication channel of the second mobile station (hereinafter referred to as the third frequency), and the first switching means The passband of the bandpass filter of the transmitter is switched to a third frequency band including the third frequency, and the receiving frequency setting means changes the receiving frequency of the first mobile station to that of the second mobile station. The transmission frequency of the specified communication channel (hereinafter referred to as the fourth frequency) is set, and the second switching means changes the passband of the bandpass filter of the receiving section to a fourth frequency that includes the fourth frequency. 1. A cordless telephone device characterized in that a wireless line is configured between the first mobile station and the second mobile station by switching to a frequency band of No. 4, and two-way communication is performed. 5. In the cordless telephone device according to claim 4, the first frequency band and the third frequency band are the same frequency band, and the second frequency band and the fourth frequency band are the same. A cordless telephone device characterized in that the frequency bands are the same frequency band.