JPH0884362A - Channel switching device for cordless telephone set - Google Patents

Abstract

PURPOSE: To provide a function for making a speech channel of a slave set match a speech channel of a host set when channel deviation between the host set and the slave set takes place. CONSTITUTION: A slave set B of a cordless telephone set to which plural channels are assigned as speech channels is provided with a carrier sense section 35 detecting the presence of a transmission radio wave from the master set at the radio channel connection with the master set through an optional speech channel and a channel changeover control section 33 selecting a preset initial speech channel or fixing the channel to a speech channel having a carrier detected through carrier sensing when the carrier sense section 35 does not detect a transmission radio wave.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cordless telephone in which a plurality of channels are assigned as a call channel, and an arbitrary channel is selected from the plurality of channels during a call to make a call. Is
The present invention relates to a channel switching device for a cordless telephone that can exit a state where a channel shift occurs between a master unit and a slave unit by a channel change function and resume a normal call.

[0002]

2. Description of the Related Art Conventionally, generally used cordless telephones are assigned a plurality of channels (for example, 10 channels) as communication channels. In such a cordless telephone, when making or receiving a call, the base unit selects a predetermined channel from a plurality of channels (usually the call channel at the end of the immediately preceding call), and the selected call. The channel is used to perform transmission / reception between the master unit and the slave unit.

By the way, when a plurality of cordless telephones of such a system are installed in a small area, when one cordless telephone which is adjacent to another operates on the same channel, transmission of one cordless telephone is performed. Radio waves may be received by one other cordless telephone.

Therefore, in the conventional cordless telephone,
When such interference occurs or reception failure due to noise or the like occurs, a channel switching key for switching a communication channel to another channel is provided in the slave. That is, when the channel switch key is pressed,
A call channel switching request signal is transmitted from the child device to the parent device. Upon receiving this switching request signal, the master unit executes a channel switching mode in which it switches to another communication channel.

That is, the base unit searches for an empty channel (for example, N channel) according to a predetermined procedure, and uses the empty channel data for shifting from the currently engaged M channel, for example, to the searched N channel. It transmits to the machine side, and then switches its own call channel from M channel to N channel.

On the other hand, when the slave unit receives the empty channel data from the master unit, it switches the communication channel with the master unit from the existing M channel to the N channel indicated by the data, and then sends the switching completion signal. Send to the master side. As a result, the master unit and the slave unit continue to talk using the N channel.

As described above, in the conventional cordless telephone, when a call failure due to interference or noise occurs, the call channel can be switched to another channel at the request of the handset.

[0008]

However, when the master unit cannot receive the switching completion signal transmitted from the slave unit after the call channel is switched by the above-mentioned procedure,
The parent device determines that the channel switching has failed, and at that time, the call channel is switched from the N channel to the M channel again.

At this time, since the slave unit has already switched to the N channel and is fixed at the N channel, in this case, a channel shift occurs between the master unit and the slave unit, and the master unit and the slave unit. There was a problem that it became impossible to continue the call. Therefore, if the user wants to continue the call, the user performs an on-hook operation by placing the slave unit in the cradle of the master unit to end the call, then picks up the slave unit again and performs a call operation to the other party's telephone. I had to do such a troublesome operation.

The present invention was devised in view of the above problems. When a channel shift between the master and the slave occurs due to the switching operation as described above, the call channel of the slave is changed to the call channel of the master. An object of the present invention is to provide a channel switching device of a cordless telephone having a matching function.

[0011]

In order to solve the above problems, a channel switching device of a cordless telephone set forth in claim 1 according to the present invention is connected to a master unit connected to a telephone line by a wireless line. It is provided with a cordless handset, and a plurality of channels are assigned as call channels. When the call is made, the present invention is applied to a cordless telephone that selects an arbitrary channel from the plurality of channels and makes a call. Is a carrier sense unit that detects the presence or absence of a transmission radio wave from the slave unit when a wireless line is connected to the slave unit by an arbitrary communication channel, and the transmission sense radio wave is not detected by the carrier sense unit. And a channel switching control unit for returning to a preset initial call channel, the slave unit is provided with When a wireless line is connected to the device, a carrier sense unit that detects the presence or absence of a radio wave transmitted from the master unit, and a preset initial value if the carrier sense unit does not detect the radio wave transmitted And a channel switching control unit for returning to the call channel. According to a second aspect of the present invention, there is provided a channel switching device for cordless telephones, which comprises a slave unit connected to a master unit connected to a telephone line by a wireless line, and has a plurality of communication channels. Is applied to a cordless telephone that selects a desired channel from a plurality of channels and makes a call when making a call. When the wireless line is connected, a carrier sense unit that detects the presence or absence of a radio wave transmitted from the slave unit, and a channel that returns to a preset initial call channel when the carrier radio unit does not detect the radio wave transmitted A switching control unit, wherein the slave unit is connected to the master unit by a call channel when a wireless line is connected to the master unit. A carrier sense unit for detecting the presence or absence of a transmission radio wave, and when the transmission radio wave is not detected by this carrier sense unit, the plurality of communication channels are sequentially switched in accordance with a predetermined order, and the switching is performed at each switching. The carrier sense unit detects the presence or absence of a transmission radio wave, and when the transmission radio wave of the base unit is detected, the channel switching control unit fixes the call channel at the time of detection.

[0012]

The operation of the channel switching device of the cordless telephone set forth in claim 1 will be described. During a call on any call channel, if the channel switch key of the cordless handset is pressed due to, for example, poor reception, the same procedure as in the past will be followed to switch to another call channel where the handset and cordless handset are empty. Transition. That is, when the channel switching key is pressed, a call channel switching request signal is transmitted from the child device to the parent device. Upon receiving this switching request signal, the master unit executes a channel switching mode in which it switches to another communication channel.

That is, the base unit searches for an empty channel (for example, N channel) in accordance with a predetermined procedure, and the empty channel data for shifting to the searched N channel from, for example, the M channel, which is currently in communication, is used as a child. It transmits to the machine side, and then switches its own call channel from M channel to N channel.

On the other hand, when the slave unit receives the empty channel data from the master unit, it switches the communication channel with the master unit from the existing M channel to the N channel indicated by the data, and then sends the switching completion signal. Send to the master side. During the execution of such a channel switching mode, the carrier sense units of the master unit and the slave unit always detect the presence or absence of the transmission radio wave of the other party.

Therefore, for example, when the switching completion signal from the slave unit is not received by the master unit due to poor reception or the like, the master unit determines that the channel switching has failed, and once switches the communication channel ( N channel)
To the initial call channel (for example, the original call channel M channel). That is, at this point, the call channel (M channel) of the parent device and the call channel (N channel) of the child device are different.

Since the carrier sense unit of the slave unit always detects the presence or absence of a transmission radio wave (hereinafter referred to as a carrier), it is possible to detect the absence of a carrier when the call channel of the master unit shifts to the M channel. Become. Therefore, in the channel switching control unit of the slave unit, based on the detection signal of no carrier from the carrier sensing unit, the own call channel is set to a preset initial call channel (in this case, the original call channel is the original call channel). M channel). As a result, the call channels of the base unit and the handset match again, so that the subsequent call can be continued.

The operation of the channel switching device of the cordless telephone set forth in claim 2 will be described. When the channel switching key of the child device is pressed due to a reception failure or the like during a telephone call on any telephone channel, the child device transmits a telephone channel switching request signal to the parent device. Upon receiving this switching request signal, the master unit executes a channel switching mode in which it switches to another communication channel.

That is, the base unit searches for an empty channel (for example, N channel) according to a predetermined procedure, and uses the empty channel data for transitioning from the currently engaged, for example, M channel to the searched N channel. It transmits to the machine side, and then switches its own call channel from M channel to N channel.

On the other hand, when the slave unit receives the empty channel data from the master unit, it switches the communication channel with the master unit from the existing M channel to the N channel indicated by the data, and then sends the switching completion signal. Send to the master side. During the execution of such a channel switching mode, the carrier sense units of the master unit and the slave unit constantly detect the presence or absence of the carrier of the partner.

Therefore, for example, if the switching completion signal from the slave unit is not received by the master unit due to poor reception or the like, the master unit judges that the channel switching has failed, and once switches the call channel ( N channel)
To the initial call channel (for example, the original call channel M channel). That is, at this point, the call channel (M channel) of the parent device and the call channel (N channel) of the child device are different. The above operation is similar to that of the first aspect.

Since the carrier sense unit of the slave unit always detects the presence / absence of a carrier, the absence of carrier is detected when the communication channel of the master unit is changed to the M channel. Therefore, the channel switching control unit of the child device sequentially switches a plurality of communication channels in accordance with a predetermined order, and at each switching,
The carrier sense unit detects the presence / absence of carriers. Then, when the carrier which is the transmission radio wave of the parent device is detected, it is fixed to the communication channel (M channel in this case) at the time of the detection.

As a result, the call channels of the master unit and the slave unit are matched again, so that the subsequent call can be continued. In this way, when the call channel of the master unit and the slave unit do not match due to the execution of the channel switch mode during a call, the channel switch control unit of the slave unit performs a plurality of call channels according to a predetermined order. If the base unit is not returned to the M channel which is the initial call channel, the carrier sense of the remaining call channels is performed in a certain order by performing the carrier sense by sequentially switching. It is possible to reliably detect the call channel that the base unit has moved to.

In other words, even if the base unit has changed to a call channel different from the initial call channel, the call channel of the handset can be surely matched with the call channel of the base unit. . According to the channel switching device for a cordless telephone according to the present invention, when a channel shift occurs between the base unit and the handset during a call, the handset is placed in the cradle of the base unit to end the call once. Instead, it becomes possible to resume such a normal call by getting out of such a channel shift state.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are block diagrams showing the electrical configurations of a master unit A and a slave unit B of a cordless telephone to which the channel switching device of the present invention is applied. In the present embodiment, the usable channel of the cordless telephone is 1
It is assumed that channels 10 to 10 are assigned.

In FIG. 1 showing the electrical configuration of the master unit A,
A speech network circuit 3 is connected to the telephone line 1 via a hook switch 2, and a wireless transceiver 5 is bidirectionally connected to the speech network circuit 3 via a speech circuit 4. In addition, the wireless transceiver 5
An antenna 6 that transmits and receives radio waves to and from the child device B is connected.

Further, an incoming call detection circuit 7 for detecting a ringing signal sent to the telephone line 1 is connected, and the output of the incoming call detection circuit 7 is output from a control circuit 10 for controlling the operation of the master A as a whole. It is connected to the master unit control unit 11. Control circuit 1
Reference numeral 0 is composed of a master unit control unit 11, a data transmission / reception control unit 12, a channel switching control unit 13, a channel storage unit 14, and a carrier sense unit 15. The master unit control unit 11, the data transmission / reception control unit 12, and the channel The switching control unit 13 and the channel storage unit 14 are bidirectionally connected to each other. In addition, in the master unit control unit 11,
The output of the carrier sense unit 15 is connected.

The data transmission / reception control unit 12 and the wireless transmission / reception unit 5 are bidirectionally connected, and the output of the channel switching control unit 13 is connected to the wireless transmission / reception unit 5. The output of the wireless transmission / reception unit 5 is connected to the carrier sense unit 15.

The master unit control section 11 controls the operation of the entire master unit A, such as line connection control and call control by incoming or outgoing calls, and when a channel switching mode is entered, a vacant channel is followed according to a certain procedure. Is a block for performing control to switch to the empty channel.

The data transmission / reception control unit 12 gives various control signals such as a call request signal from the handset B and a channel switching request signal received by the reception unit of the radio transmission / reception unit 5 to the base unit control unit 11. , A block for outputting various control signals such as a line connection signal for the slave B and a channel switching signal to the transmitter of the wireless transmitter / receiver 5.

The channel switching control unit 13 sets the carrier frequency of the wireless transmission / reception unit 5 to the frequency of the empty channel searched by the channel switching mode,
This block controls the switching of call channels. The channel storage unit 14 is a block that stores the call channel at the end of the immediately preceding call as the initial call channel, and each time a call is made, the stored data is sequentially rewritten and stored as the data of the call channel at the end of the call. It is supposed to do.

The carrier sense unit 15 includes a master unit A and a slave unit B.
This is a block that detects the presence or absence of a carrier and sends the detection signal to the master unit control unit 11 when a wireless line is connected to the device or when the channel switching mode is executed during a call.
In the above configuration, the master unit control unit 11, the data transmission / reception control unit 12, and the channel switching control unit 13 are configured to include software that operates on a computer.

On the other hand, in FIG. 2 showing the electrical configuration of the slave unit B, an antenna 21 for transmitting and receiving radio waves to and from the master unit A is shown.
A call circuit 23 is bidirectionally connected to the wireless transmitter / receiver 22 to which the microphone 2 is connected.
4 is connected to the input of the speaker 25.

The key operation unit 40 is provided with dial keys, various function keys such as calling and stopping, and a channel switching key 41 for switching a call channel to an arbitrary call channel during a call. The output of the key operation unit 40 including the channel switching key 41 is connected to the child device control unit 31 of the control circuit 30 that controls the operation of the entire child device B.

The control circuit 30 comprises a slave unit control unit 31, a data transmission / reception control unit 32, a channel switching control unit 33, a channel storage unit 34, and a carrier sense unit 35, and data transmission / reception with the slave unit control unit 31. Control unit 3
2, channel switching control unit 33 and channel storage unit 3
Each of 4 and 4 is a bidirectional connection. Further, the output of the carrier sense unit 35 is connected to the slave unit control unit 31. Further, the data transmission / reception control unit 32 and the wireless transmission / reception unit 22 are bidirectionally connected, and the output of the channel switching control unit 33 is connected to the wireless transmission / reception unit 22. The output of the wireless transmission / reception unit 22 is connected to the carrier sense unit 35.

The slave unit control section 31 controls the operation of the entire slave unit B such as call control by incoming or outgoing calls, and when it receives the empty channel data from the master unit A, it sets its own call channel to that data. It is a block that controls to switch to the call channel shown in. The data transmission / reception control unit 32 provides the slave unit control unit 31 with various control signals such as empty channel data from the base unit A received by the reception unit of the wireless transmission / reception unit 22 and requests the base unit A to switch the communication channel. It is a block that outputs various control signals such as signals to the transmission unit of the wireless transmission / reception unit 22.

The channel switching control unit 33 becomes a block for controlling the switching of the communication channel by setting the carrier frequency of the wireless transmission / reception unit 22 to the frequency of the empty channel indicated by the empty channel data from the base unit A. ing. Further, it is a block that controls the switching of the current communication channel to the initial communication channel based on the detection signal from the carrier sense unit 35 or sequentially switches the communication channels according to a predetermined order to perform carrier sense. .

The channel storage unit 34 is a block for storing the call channel at the end of the immediately preceding call as an initial call channel, and the stored data is sequentially set to the data of the call channel at the end of the call each time a call is made. It is designed to be rewritten and stored. As a result, the channel storage unit 34 of the child device B and the channel storage unit 14 of the parent device A always store the same communication channel data. The carrier sense unit 35 detects the presence / absence of a carrier at the time of connecting a wireless line between the master unit A and the slave unit B, at the time of executing a channel switching mode during a call, and the like, and detects the detection signal as a slave unit control unit 31. It is a block to be sent to.

In the above structure, the slave unit control section 3
1, the data transmission / reception control unit 32 and the channel switching control unit 33 are configured to include software operating on a computer.

Next, one embodiment of the operation of the cordless telephone having the above configuration (this is referred to as Embodiment 1) will be described with reference to FIGS.
This will be described with reference to the respective flowcharts of the parent device A and the child device B shown in FIG. The present embodiment corresponds to claim 1. Channel storage units 14, 34 of the master unit A and the slave unit B
The call channel at the end of the immediately preceding call is stored as the initial call channel. In this embodiment, for example, one channel is stored as the initial call channel.

In this state, when a ringing signal is sent through the telephone line 1, this ringing signal is detected by the incoming call detection circuit 7 and the incoming call detection signal is output. In the base unit control unit 11, based on this incoming call detection signal,
The channel switching control unit 13 sets the frequency of the wireless transmission / reception unit 5 to the frequency stored in the channel storage unit 14 (that is, one channel which is the initial call channel), and the data transmission / reception control unit 12 wirelessly transmits / receives an incoming call detection signal. The data is transmitted from the unit 5 to the child device B side. Further, in the base unit control unit 11, based on this incoming call detection signal,
The hook switch 2 is off-hooked to connect to the telephone line 1 (steps 51 and 52).

On the other hand, in the handset B, the incoming / outgoing detection signal is received by the wireless transmission / reception section 22, and the data transmission / reception control section 32 is received.
It is given to the child device control unit 31 via. The handset controller 31
Based on this incoming detection signal, the channel switching control unit 33
The frequency of the wireless transmission / reception unit 22 is set to the frequency stored in the channel storage unit 34 (that is, one channel which is the initial call channel) (step 71).
As a result, both the master unit A and the slave unit B are set to one channel, so that the slave unit B can communicate with the outside line via the master unit A (steps 53 and 72).

In this call state, when the adjacent cordless telephone operates on the same channel, interference occurs, or reception failure occurs due to noise or the like, the user of the slave unit B The channel switching key 41 of the key operation unit 40 is pressed. Handset control unit 31
On the basis of this key operation signal, the data transmission / reception control unit 3
2 to transmit a call channel switching request signal to the base unit A from the wireless transmission / reception unit 22 (step 7).
3, 74).

This transmitted radio wave is received by the wireless transmission / reception unit 5 of the base unit A and given to the base unit control unit 11 via the data transmission / reception control unit 12 (step 54). Base unit control unit 1
In No. 1, the channel switching mode for shifting to another communication channel is executed based on this switching request signal.

That is, the master unit control section 11 searches for an empty channel in order from the channel 10 side, for example, in accordance with a predetermined procedure (step 55). The search for an empty channel is performed by detecting the presence or absence of carriers by the carrier sense unit 15. Here, in this embodiment, it is assumed that 10 channels are empty channels. Base unit control unit 11
Then, the empty channel data indicating the searched empty channel 10 is transmitted to the handset B side (step 56), and then the channel switching control unit 13 is controlled to set its own call channel to the previous one channel. To 10 channels (step 57).

This transmitted radio wave is transmitted to the wireless transmitter / receiver 22 of the handset B.
And is given to the handset controller 31 via the data transmission / reception controller 32. In the child device control unit 31, the channel switching control unit 33 is based on this empty channel data.
Is controlled to switch and fix its own communication channel from the previous one channel to the ten channels indicated by the data (step 78). After that, the switching completion signal is transmitted to the master unit A side (step 79). In the handset B, when the call ends or a predetermined time elapses after the switching request signal is transmitted until the empty channel data is received from the base A, the call ends at that time ( Steps 76, 77).

This transmitted radio wave is received by the wireless transmission / reception unit 5 of the master unit A and given to the master unit control unit 11 via the data transmission / reception control unit 12 (step 58). Base unit control unit 1
In No. 1, on the basis of this switching completion signal, the communication channel is fixed to the switched 10 channels. As a result, since both the base unit A and the base unit B are fixed to the 10th channel, the base unit B can continue the call with the outside line (step 62).

By the way, when the switching completion signal transmitted from the slave unit B is not received by the master unit A due to some radio interference, the master unit A follows a predetermined procedure to switch the call channel (10 channels). ) Is switched to the original 1 channel again and fixed (steps 58 and 5).
9, 60, 61) At this time, on the side of the handset B, it is already 10
Since the channel has been switched to and fixed at 10 channels, it means that a channel shift has occurred between the master unit A and the slave unit B.

Since the carrier sense unit 35 of the handset B always detects the presence or absence of the carrier, it detects the absence of the carrier when the call channel of the base A shifts to 10 (step 80). ).

The slave unit control unit 31 controls the channel switching control unit 33 based on the detection signal indicating that there is no carrier, and changes the communication channel switched to 10 channels,
Switch to the original 1-channel communication channel (step 81). As a result, the communication channel between the master unit A and the slave unit B is matched again with one channel.
The channel allows subsequent calls to continue.

After this, when the call ends, the call channels at the end of the call are stored as the initial call channels in the channel storage units 14 and 34 of the master unit A and the slave unit B, respectively. For example, when the call is ended after switching to channel 10 and continuing the call, channel 10 is stored in each channel storage unit 14 and 34 as the initial call channel. Further, when the call is terminated in a state where the original channel 1 is restored, the original channel 1 is stored in each channel storage unit 14 and 34 as the initial call channel.

Next, another embodiment of the operation of the cordless telephone of the present invention (this will be referred to as Embodiment 2) will be described with reference to the flowchart of the handset B shown in FIG. The present embodiment corresponds to claim 2. The operation of base unit A is
Since the operation is the same as that shown in FIG. 3, description thereof will be omitted here. The operation of the handset B is different from that of the first embodiment only in the step 81 shown in FIG. 4. Therefore, FIG. 5 shows an operation flowchart of only the part corresponding to the step 81. ing.

That is, in this embodiment, the operation of the child device B is exactly the same as the operation from step 71 to step 80 shown in FIG.
The description of the operation up to step 80 is omitted. Then, if it is detected in step 80 that there is no carrier, the operation proceeds to step 91.

That is, the slave unit control unit 31 controls the channel switching control unit 33 based on the detection signal indicating that there is no carrier, and a predetermined order (for example, 10 channels, 9 channels ...) In accordance with the above, control for sequentially switching a plurality of call channels is performed (step 9).
1). Then, each time the switching is performed, the carrier sense unit 3
The presence or absence of carriers is detected by 5 (step 92).

As a result of repeating the processing of steps 91 and 92, when the carrier of the base unit A is detected,
The telephone call channel at the time of the detection (in this case, the original channel 1) is fixed (step 93). As a result, the call channels of the master unit A and the slave unit B match again, so that the subsequent call can be continued.

In this way, when the channel shift occurs, if the slave unit B is configured to sequentially perform carrier sensing, the base unit A shifts to a call channel different from the initial call channel for some reason. Even in this case, the call channel of the slave B can be surely matched with the call channel of the master A.

Next, still another embodiment of the operation of the cordless telephone of the present invention (referred to as Embodiment 3) will be described with respect to each of the master unit A and the slave unit B shown in FIGS. 6 and 7. This will be described with reference to the flowchart. This embodiment also corresponds to claim 2. Also, with respect to the master unit A, the operation differs from that of the first embodiment only in the part of step 61 shown in FIG. 3, and therefore FIG. 6 shows an operation flowchart of only the part corresponding to this step 61. ing. The operation of the handset B is different from that of the first embodiment only in the step 81 shown in FIG. 4. Therefore, FIG. 7 shows an operation flowchart of only the part corresponding to the step 81. ing. Therefore, in the following description, only the operation of the parts corresponding to these will be described.

That is, in the master unit A, it is determined that the switching completion signal transmitted from the slave unit B is not received by the master unit A due to some radio interference due to the processing in steps 58, 59 and 60 shown in FIG. If so, the operation proceeds to step 101.

In this case, instead of shifting to a predetermined initial communication channel, a predetermined order (for example, 10 channels, 9 channels ...
In this order, the call channels are sequentially switched to search for an empty channel. That is, the carrier sense unit 15 detects the presence or absence of a carrier each time the call channel is switched (step 102). As a result of repeating the processing of steps 101 and 102, when an empty carrier is detected, it is fixed to the communication channel (for example, two channels) at the time of the detection (step 10).
3).

In this way, when a reception failure occurs,
Instead of simply returning to the original initial call channel, base unit A
By performing carrier sense on the side as well, it is possible to shift to a call channel that is completely empty without radio interference.

On the other hand, in the slave unit B, step 8 shown in FIG.
When it is detected that there is no carrier at 0, the operation proceeds to step 111. That is, the handset controller 31
Controls the channel switching control unit 33 on the basis of the detection signal indicating that there is no carrier, and sequentially switches a plurality of communication channels in a predetermined order (for example, 10 channels, 9 channels, ...). Is performed (step 111). Then, every time the switching is performed, the presence or absence of carriers is detected by the carrier sense unit 35 (step 112).

As a result of repeating the processing of steps 111 and 112, when the carrier of the master unit A is detected, it is fixed to the communication channel (two channels in this case) at the time of the detection (step 113). .

As a result, the call channels of the master unit A and the slave unit B match again, so that it becomes possible to continue the subsequent call. With such a configuration, the call channel of the slave unit B can be surely matched with the call channel of the master unit A, no matter which call channel the master unit A shifts to.

As described above, according to the channel switching device of the cordless telephone according to the present invention, even if the channel shift between the master unit A and the slave unit B occurs during a call,
It is possible to get out of the channel shift state and resume a normal call without temporarily ending the call.

In the above embodiment, the empty channel is searched from the 10th channel side, but how to search for the empty channel can be set arbitrarily. For example, when the initial call channel is one channel, it is possible to search in the order of two channels, three channels, ... In reverse of the above embodiment. It is also possible to search at random using a random number table or the like.

[0065]

The channel switching device of the cordless telephone according to the present invention can perform the carrier sense on the slave unit side even if the channel shift between the master unit and the slave unit occurs during a call, and the transferred master unit can be operated. Since it can be matched with the call channel, the call can be restarted without disconnecting the connected line.
Further, it is not necessary to put the child device in the cradle of the parent device to resume the call.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a base unit of a cordless telephone to which a channel switching device of the present invention is applied.

FIG. 2 is a block diagram showing an electrical configuration of a cordless telephone handset to which the channel switching device of the present invention is applied.

FIG. 3 is a flowchart for explaining one embodiment (embodiment 1) of the operation of the base unit of the cordless telephone to which the channel switching device of the present invention is applied.

FIG. 4 is a flowchart for explaining one embodiment (embodiment 1) of the operation of the cordless telephone set to which the channel switching device of the present invention is applied.

FIG. 5 is a flowchart for explaining another embodiment (embodiment 2) of the operation of the cordless telephone handset to which the channel switching device of the present invention is applied.

FIG. 6 is a flow chart for explaining another embodiment (third embodiment) of the operation of the parent device of the cordless telephone to which the channel switching device of the present invention is applied.

FIG. 7 is a flowchart for explaining another embodiment (third embodiment) of the operation of the cordless telephone set to which the channel switching device of the present invention is applied.

[Explanation of symbols]

 A master unit B slave unit 10 control circuit 11 master unit control unit 12 data transmission / reception control unit 13 channel switching control unit 14 channel storage unit 15 carrier sense unit 30 control circuit 31 master unit control unit 32 data transmission / reception control unit 33 channel switching control unit 34 channel storage section 35 carrier sense section 41 channel switching key

Claims (2)

[Claims] 1. A main unit connected to a telephone line is provided with a slave unit connected by a wireless line, and a plurality of channels are assigned as call channels. In a cordless telephone that selects a desired channel from among the cordless telephones to make a call, the base unit determines whether or not there is a radio wave transmitted from the handset when a wireless line is connected to the handset by an arbitrary call channel. And a channel switching control unit for returning to a preset initial call channel when the transmitted radio wave is not detected by the carrier sense unit, and the slave unit is an arbitrary call channel. And a carrier sense unit that detects the presence or absence of a radio wave transmitted from the master unit when a wireless line is connected to the master unit. Channel switching device of a cordless telephone, characterized in that a channel switch control unit to return to the initial communication channel that has been set in advance in the case of not detecting the transmission radio wave by Nsu unit. 2. The channel switching control unit of the slave unit sequentially switches the plurality of call channels according to a predetermined order when the carrier sense unit does not detect the transmission radio wave of the master unit, 2. The cordless telephone according to claim 1, wherein the presence or absence of a transmission radio wave is detected by the carrier sense unit at each switching, and when the transmission radio wave of the master unit is detected, it is fixed to the communication channel at the time of the detection. Channel switching device.