JPH09224269A - Pushbutton telephone system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pushbutton telephone system in which a speech opposite party feels no unpleasantness and the reliability of a cordless telephone set is enhanced. SOLUTION: On the occurrence of a communication error caused during transmission of external line LED information attended with external line call of other extension or a communication error when a reception electric field strength of a master set 2 below a radio channel interrupt level is consecutive for a prescribed time, after the radio channel interruption processing attended with the communication error, a master set 1 conducts processing for system holding based on the error notice. In this hold processing, a sound source 14 is connected to an external line i/f circuit 11 under the control of a switch circuit 12 by a control section 15 and the sound source 14 sends a hold tone to an external line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a button telephone system that accommodates a cordless telephone as an extension telephone.

[0002]

2. Description of the Related Art Generally, in a key telephone system that accommodates a cordless telephone as an extension telephone, when a cordless telephone detects an out-of-range movement of a cordless handset, or a radio transmission error occurs between the cordless handset. If it occurs, disconnect the wireless line unilaterally from the data transmission side,
At the data receiving side, control is performed so as to detect the carrier disconnection due to the disconnection of the wireless line and stop the transmission of radio waves.

Further, when the radio line is disconnected on the base unit side, if there is an outside line during a call, the outside line is set to be disconnected at the same time.

[0004]

However, in the above-mentioned conventional button telephone system, if there is an outside line that is busy when the wireless line is disconnected on the base unit side, the outside line is also disconnected. Suddenly the call to the outside line of the other party is interrupted, causing the outside line of the other party to feel uncomfortable. In addition, even for cordless telephone users, the temporary deterioration of wireless conditions may result in sudden disconnection of the busy line, which may lead to loss of important business opportunities. is there.

In particular, compared to home cordless telephones,
In the key telephone system, a lot of control data is transmitted over the wireless line even during a call, such as external line information and display data that change sequentially depending on other extension conditions. When the call is not performed, the party in the call thinks that it is simply a sudden disconnection of the call line without recognizing the deterioration of the radio condition, and the call origination operation is performed again by the party. However, since there is a time lag between detecting the carrier disconnection and stopping the transmission of radio waves between the parent and child handsets, in the above-mentioned case, it is not possible to re-call from the child handset for a while and the cordless phone Trust will be lost.

An object of the present invention is to provide a button telephone system which can prevent the other party from feeling uncomfortable and can improve the reliability of the cordless telephone.

[0007]

According to the first aspect of the present invention,
In a button telephone system accommodating a cordless telephone as an extension telephone, a wireless communication means for relaying control data exchanged between a parent device and a child device of the cordless telephone via a call channel, and the wireless communication means. When a communication error occurs in relaying the control data transmitted from the master unit to the slave unit, a holding unit is provided for putting a telephone line during a call into a system holding state.

According to a second aspect of the present invention, in the key telephone system according to the first aspect, a disconnecting means for disconnecting a wireless line between the parent and child devices in which the communication error has occurred, and a wireless communication between the parent and child devices by the disconnecting means. Before disconnecting the line, when a warning line for sending a warning sound to the slave unit and a wireless line disconnection between the parent and slave units by the disconnecting unit are performed, the user of the slave unit is notified of the disconnection of the wireless line. And a notification means.

According to a third aspect of the present invention, in the button telephone system according to the first aspect, when the communication error occurs, a notification to that effect is sent to the main device that controls the connection between the cordless telephone and the outside line. It is characterized by comprising means.

According to a fourth aspect of the present invention, in the key telephone system according to the first aspect, when the holding means puts the telephone line in a call on the system holding state, the cordless telephone to which the communication error has occurred is sent to the master unit. When the instruction means for instructing the connection of the wireless line and the master unit succeeds in the connection of the wireless line on the basis of the instruction of the instructing means, it is confirmed that there is an outside line on hold in the cordless telephone handset having the communication error. It is characterized by comprising a notification means for informing.

According to a fifth aspect of the present invention, in the key telephone system according to the first aspect, when the holding means puts the telephone line in a call on the system hold state, the standby state is different from that of the cordless telephone in which the communication error occurs. The cordless telephone set is provided with notifying means for notifying extension information indicating the occurrence of the communication error and outside line information indicating the held telephone line.

According to a sixth aspect of the present invention, in the key telephone system according to the first aspect, the holding means is different from the display in the system holding state of the telephone line during the call by the system holding operation from the slave unit. It is characterized by further comprising control means for controlling the slave unit so as to perform a display in a system hold state of a telephone line during a call.

According to a seventh aspect of the present invention, in a button telephone system accommodating a cordless telephone as an extension telephone, a measuring means for measuring a received electric field strength of a radio wave transmitted from a cordless telephone to a base unit at a constant cycle. When,
When the measurement result by the measuring means indicates the received electric field strength below the wireless line disconnection level, the time measuring means for measuring the duration of the received electric field strength below the wireless line disconnection level, the measurement result by the measuring means and the time measuring means If it is determined from the time measurement result that the state below the wireless line disconnection level of the received electric field strength in the master unit continues for a predetermined time,
It is characterized by comprising a holding means for judging that a communication error has occurred and for putting a telephone line during a call into a system holding state.

According to an eighth aspect of the present invention, in the key telephone system according to the seventh aspect, a disconnecting unit disconnects a wireless line between the parent and child units in which the communication error occurs, and a wireless communication between the parent and child units by the disconnecting unit. Before disconnecting the line, when a warning line for sending a warning sound to the slave unit and a wireless line disconnection between the parent and slave units by the disconnecting unit are performed, the user of the slave unit is notified of the disconnection of the wireless line. And a notification means.

According to a ninth aspect of the present invention, in the button telephone system according to the seventh aspect, when the communication error occurs, a notification to that effect is sent to the main device that controls the connection between the cordless telephone and the outside line. It is characterized by comprising means.

According to a tenth aspect of the present invention, in the key telephone system according to the seventh aspect, when the holding means puts the telephone line in a call on the system holding state, the cordless telephone having the communication error is sent to the master unit. When the instruction means for instructing the connection of the wireless line and the master unit succeeds in the connection of the wireless line on the basis of the instruction of the instructing means, it is confirmed that there is an outside line on hold in the cordless telephone handset having the communication error. It is characterized by comprising a notification means for informing.

According to an eleventh aspect of the present invention, in the key telephone system according to the seventh aspect, when the holding means puts the telephone line in a call on the system holding state, the waiting state is different from that of the cordless telephone in which the communication error occurs. The cordless telephone set is provided with notifying means for notifying extension information indicating the occurrence of the communication error and outside line information indicating the held telephone line.

According to a twelfth aspect of the present invention, in the button telephone system according to the seventh aspect, the display by the holding means is different from the display in the system holding state of the telephone line during the call by the system holding operation from the handset. It is characterized by further comprising control means for controlling the slave unit so as to perform a display in a system hold state of a telephone line during a call.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a key telephone system of the present invention.

As shown in FIG. 1, the key telephone system includes a main unit 1 for controlling connection switching with an outside line and a master unit 2.
And a child device 3 which is an extension telephone, and a parent device 2 and a child device 3
And cooperate with each other to form a cordless telephone.

The main unit 1 is an external line i / f circuit (external line interface circuit) 1 having an interface with a telephone line 4.
1, a switch circuit 12 for connecting a communication path, an extension i / f circuit (extension interface circuit) 13 having an interface with an extension terminal, a sound source 14 for providing various service sounds including a hold tone, and a main device 1 It has the control part 15 which controls the whole.

The master unit 2 is configured to send control information and the like from the main unit 1 to the slave unit 3 and send control information and the like from the slave unit 3 to the main unit 1.

The base unit 2 has a line i / f circuit (line interface circuit) 21 for controlling communication with the main unit 1, and a signal processing unit 22 for performing signal conversion between wired and wireless.
And a wireless circuit 23 that transmits and receives wireless signals via the antenna 24. The level of the strength of the radio wave received by the wireless circuit 23 is measured by the reception level measuring unit 25,
The control unit 26 controls the entire base unit 2.

The handset 3 has a radio circuit 32 for transmitting and receiving radio waves via the antenna 31, and a signal processing unit 33 for performing processing such as mutual conversion between radio signals and voice signals. The audio signal output from the unit 33 is converted into audio by the speaker 35 and output. An audio signal is input to the signal processing unit 33 from the microphone 36, and the microphone 36 inputs the audio and converts the audio into the audio signal. The control of the entire slave unit 3 is performed by the control unit 34, and various information indicating the control content, connection destination, etc. is displayed on the LCD display 37.

Next, the processing operation when a radio failure occurs in this key telephone system will be described with reference to FIGS. 2 and 3. 2 and 3 are flowcharts showing the processing operation when a radio failure occurs in the button telephone system of FIG. In the present description, an example of the processing operation will be described in the case where the handset 3 has a radio failure due to external noise during a call with the outside line (1).

First, in the master unit 2, as shown in FIG. 2, the control unit 26 monitors whether or not a communication error has occurred on the wireless line connected to the slave unit 3 (step). S1). This monitoring is performed based on the wireless condition of the wireless circuit 23 and the measurement result of the strength of the radio wave received by the wireless circuit 23 by the reception level measuring unit 25, and the presence or absence of a communication error is detected. The communication error detected by this monitoring is a communication error or the like that occurs during transmission of the outside line LED information associated with the outside line transmission of another extension line. The process of step S1 includes the reception electric field strength of the base unit 2. When the state below the wireless line disconnection level continues for a predetermined time, a process for determining that a communication error has occurred is not included, and this determination process will be described later in step S.
It is performed in the processing after 8.

When a communication error such as a communication error occurring during transmission of the outside line LED information due to the outside line transmission of another extension line is detected, an error notification process is performed by the control unit 26 (step S2). In this error notification process, an error notification indicating that a communication error has occurred is sent from the control unit 26 to the line i /
It is sent to the main unit 1 via the f circuit 21.

In the main unit 1, the error notification sent from the master unit 2 is input to the control unit 15 via the extension i / f circuit 13, and the control unit 15 starts the timer in response to the error notification input (step S3).

Simultaneously with the start of this timer, the switch circuit 12 is controlled by the control unit 15 so as to send the warning sound generated from the sound source 14 to the slave unit 3 via the master unit 2,
The sending of the warning sound to the handset 3 is started (step S
4).

When the sending of the warning sound is started, the timer time is monitored (step S5), and when the warning sound is sent to the slave unit 3 through the master unit 2 for a predetermined time, the switch circuit 1
By controlling 2 (step S6), the output of the warning sound to the handset 3 is stopped.

After the sending of the warning sound is stopped, the control unit 15 gives an instruction to the base unit 2 via the extension i / f circuit 13 to disconnect the wireless line with the handset unit 3, and the disconnection process is performed based on the instruction. Is performed (step S7).

Specifically, in this disconnection process, the control unit 26, which has received the wireless line disconnection parent instruction via the wireless i / f circuit 21, transfers the wireless line disconnection master instruction to the slave unit 3 via the signal processing unit 22 and the wireless circuit 23. After notifying that the wireless line is forcibly disconnected, the radio wave transmission to the handset 3 is stopped after the notification. On the other hand, when the handset 3 receives a message that the wireless line is forcibly disconnected,
In the slave unit 3, the notification is sent to the control unit 3 via the wireless circuit 32.
4, the control unit 34 controls to display information indicating that the wireless line is forcibly disconnected due to the wireless failure occurrence on the LCD display unit 37 based on the notification.
Control to stop sending radio waves. If the above-mentioned disconnection notification is not received by the handset 3 due to noise or the like, the handset 3 stops the transmission of radio waves due to the known detection of carrier disconnection.

If the occurrence of a communication error is not detected (step S1), the radio circuit 23 by the reception level measuring section 25 is detected.
The control unit 26 determines whether the received electric field strength in the wireless circuit 23 is equal to or lower than the disconnection level based on the measurement result for the strength of the radio wave received in step S8, and the received electric field strength in the wireless circuit 23 is If it is higher than the cutting level, the process returns to step S1 again.

On the other hand, if the received electric field strength in the radio circuit 23 of the base unit 2 is below the disconnection level, the control unit 26
Starts the timer it has (step S
9) If the received electric field strength in the wireless circuit 23 becomes higher than the disconnection level by the time the timer measures the predetermined time (steps S10 and S11), the operation of the timer is stopped (step S12). After the timer is stopped, the process returns to step S1 again.

If the received electric field strength in the radio circuit 23 is below the disconnection level (steps S10 and S11) until the timer completes counting the predetermined time (steps S10 and S11), it is determined that a communication error has occurred, and The processing from step S2 described above is performed.

As described above, communication in the case where a communication error occurred during transmission of outside line LED information due to an outside line transmission of another extension line and a state where the received electric field strength in the base unit 2 is below the wireless line disconnection level continues for a predetermined time. After the wireless line disconnection process due to the error, as shown in FIG. 3, the main device 1 performs a process for system hold based on the error notification.

First, the switch circuit 12 by the control unit 15
By the control of 1, the sound source 14 and the outside line i / f circuit 11 are connected, and the hold sound is sent from the sound source 14 to the outside line (1) (step S13).

Next, the LEDs representing the outside line (1) in all other base units 3 and extension telephones (including general extension telephones) except for the cordless telephone in which the error has occurred,
An instruction to blink in red to indicate that the outside line (1) is on hold is given from the control unit 15 to all other base units 3 and extension telephones via the extension i / f circuit 13 (step S14). ).

After the LED blinks in red, the extension telephone number in error and the extension telephone number in hold are displayed for all extension telephones in the standby state except the cordless telephone in which the error has occurred. An instruction is issued from the control unit 15 via the extension i / f circuit 13 (step S15).

Then, the control unit 15 issues an instruction to connect the wireless line to the corresponding slave unit 3 via the extension i / f circuit 13 to the master unit 2 in which the error has occurred, and the line i / f The control unit 26, which has received the wireless line connection instruction via the f circuit 21, performs the processing via the signal processing unit 22 and the wireless circuit 23 (step S16).

Subsequently, when the slave 3 and the wireless line are normally connected (step S17), an error occurs in the master 2
A display processing instruction indicating that the outside line (1) is on hold is issued (step S18).

Specifically, the LED indicating the outside line (1) in the child device 3 is set to the green blinking state indicating that the user himself has held it, and the LCD display 37.
In order to display that the outside line (1) is on hold due to the occurrence of a wireless failure, the control unit 15 issues an instruction to the master unit 2 via the extension i / f circuit 13. Send this instruction to line i / f
The master unit 2 received via the circuit 21 transmits the instruction content to the slave unit 3 via the signal processing unit 22 and the wireless circuit 23 via a wireless line. In the child device 3, the above-mentioned instruction content is transmitted to the wireless circuit 32.
To the control unit 34 so that the LED representing the external line (1) is in a blinking green state on the basis of the above-mentioned instruction content, and the LCD display 37 is connected to the external line due to a wireless failure. Control is performed so that (1) indicates that the call is on hold, and that the speaker 35 emits a sound indicating that the wireless failure has been restored. As described above, in the present embodiment, in the case of system hold due to an error occurrence, the cordless telephone is controlled so as to display a system hold different from the so-called normal system hold due to the hold operation in the handset 3, so that the hold responder Will be able to respond accordingly.

If the wireless line connection process to the handset 3 fails (step S17), the connection of the wireless line between the parent and handset in which the error has occurred is abandoned, and the process of step S18 is not executed.

After the display processing indicating that the outside line (1) is on hold, or when the connection of the wireless line between the parent and child device in which the error has occurred is abandoned, the extension telephone that responds to the outside line (1) on hold. It is monitored whether or not there is (step S
19).

When there is an extension telephone that responds to the held outside line (1), a call path connection process between the extension telephone and the outside line (1) is performed (step S20). Specifically, the control unit 15 controls the switch circuit 12 to establish a call path connection between the outside line (1) and the extension telephone that responds to the outside line (1).

Next, since the call state between the outside line (1) and the extension telephone that responds to the extension line (1) is obtained by the above-mentioned call path connection, the LEDs of the other extension telephones are turned on so that the LED of the extension telephone is lit in green. An instruction is issued from the control unit 15 to all the extension lines via the extension i / f circuit 13 so that the red light is turned on (step S21).

After the display processing of the LED representing the outside line (1), the standby state display processing is performed (step S22). In this standby state display processing, in step S15, a standby display state such as a clock display state is set for the extension telephone in the standby state instructed to display the extension telephone number in which an error has occurred and the external telephone number in the hold state. An instruction to return is issued.

As described above, when a communication error or the like due to a fault on the wireless line occurs, the outside line (1) during a call is kept in a hold state without being disconnected, so that the cordless handset 3 is connected to the wireless line again. If it is possible, the user of the cordless handset 3 can make a hold response to the outside line (1) once the call is cut off, and when the cordless handset 3 cannot be connected to the wireless line again, another extension telephone can be used. With the hold response, the call with the outside line (1) can be made again, and it is possible to prevent the other party from feeling uncomfortable and to improve the reliability of the cordless telephone.

[0050]

As described above, according to the button telephone system of the first aspect, the control data exchanged by the wireless communication means between the base unit and the handset of the cordless telephone via the call channel. When a communication error occurs in relaying the control data sent from the master unit to the slave unit by the wireless communication unit by the relay unit, the telephone line during the call is put in the system hold state, so On the other hand, it is possible to make a hold response, to prevent the other party from feeling uncomfortable, and to improve the reliability of the cordless telephone.

According to the button telephone system of the second aspect, a disconnecting means for disconnecting the wireless line between the parent and child devices in which a communication error has occurred and a warning to the child device before disconnecting the wireless line between the parent and child devices by the disconnecting means. Since a warning means for sending a sound and a notification means for notifying the user of the slave unit of the disconnection of the wireless line when the wireless line disconnection between the parent and child units are made by the disconnecting means are provided, a communication error may occur. It is possible to notify the handset user of the disconnection of the wireless line in advance.

According to the button telephone system of the third aspect, when a communication error occurs, notification means is provided for notifying the main device which controls the connection between the cordless telephone and the outside line to that effect. It is possible to easily obtain the holding state of the outside line without disconnecting the cordless telephone from the outside line.

According to the button telephone system of the fourth aspect, when the holding means puts the telephone line in a call on the system holding state, an instruction for instructing the base unit of the cordless telephone in which a communication error has occurred to connect the wireless line. Means and a notification means for notifying that there is an external line on hold to the child device of the cordless telephone in which a communication error has occurred, when the parent device succeeds in connecting the wireless line based on the instruction of the instruction device. If the cordless handset can be connected to the wireless line again, the cordless handset user can make a hold response to an external line once the call is disconnected, and if the cordless handset cannot be connected to the wireless line again, another extension telephone The call from the outside line can be made again by the hold response from.

According to the button telephone system of the present invention, when the holding means puts the telephone line in a call on hold in the system, a communication error occurs in a cordless telephone in a standby state different from the cordless telephone in which the communication error has occurred. Since there is a notification means for notifying the extension information indicating the call and the outside line information indicating the held telephone line, the user of the cordless telephone in the standby state is provided with the extension information indicating the occurrence of a communication error and the outside line indicating the held telephone line. Information and information can be given.

According to the button telephone system of the sixth aspect, the display in the system hold state of the telephone line during call by the holding means is different from the display in the system hold state of the telephone line during call by the system hold operation from the handset. Since the control means for controlling the slave unit is provided so as to perform the above, it becomes possible for the hold responder to take a response according to the occurrence of the communication error.

According to the button telephone system of the present invention, the measuring means measures the received electric field strength of the radio wave transmitted from the cordless telephone handset to the base unit at a constant cycle, and the time measuring means uses the measuring means. When the measurement result shows the received electric field strength below the wireless line disconnection level, the duration of the received electric field strength below the wireless line disconnection level is timed, and the holding means measures the measured result by the measuring means and the timed result of the time measuring means. If it is judged that the state below the wireless line disconnection level of the received electric field strength at the device continues for a predetermined time, it is judged that a communication error has occurred, and the telephone line during the call is put on the system hold state. It is possible to make a response, to prevent the other party from feeling unpleasant, and to improve the reliability of the cordless telephone. Kill.

According to the button telephone system of the present invention, disconnection means for disconnecting the wireless line between the parent and child devices in which a communication error has occurred, and a warning to the child device before the disconnection means disconnects the wireless line between the parent and child devices. Since a warning means for sending a sound and a notification means for notifying the user of the slave unit of the disconnection of the wireless line when the wireless line disconnection between the parent and child units are made by the disconnecting means are provided, a communication error may occur. It is possible to notify the handset user of the disconnection of the wireless line in advance.

According to the button telephone system of the ninth aspect, when the communication error occurs, the notification means is provided for notifying the main device for controlling the connection between the cordless telephone and the outside line. It is possible to easily obtain the holding state of the outside line without disconnecting the cordless telephone from the outside line.

According to the button telephone system of the tenth aspect, an instruction for instructing the base unit of the cordless telephone, in which a communication error has occurred, to connect the wireless line when the telephone line in the call is put on the system hold state by the holding means. Means and a notification means for notifying that there is an external line on hold to the child device of the cordless telephone in which the communication error has occurred, when the parent device succeeds in connecting the wireless line based on the instruction of the instruction device. , If the cordless handset can be reconnected to the wireless line, the cordless handset user can make a hold response to an outside line once the call is disconnected, and if the cordless handset cannot be connected to the wireless line again, another extension line can be used. The hold response from the telephone enables the call to the outside line again.

According to the button telephone system of the eleventh aspect, when the holding means puts the telephone line in a call on the system hold state, a communication error occurs in the cordless telephone in the standby state different from the cordless telephone in which the communication error has occurred. Since there is a notification means for notifying the extension information indicating the call and the outside line information indicating the held telephone line, the user of the cordless telephone in the standby state is provided with the extension information indicating the occurrence of a communication error and the outside line indicating the held telephone line. Information and information can be given.

According to the button telephone system of the twelfth aspect, a display in the system hold state of the telephone line during call by the holding means, which is different from the display in the system hold state of the telephone line during call by the system hold operation from the handset. Since the control means for controlling the slave unit is provided so as to perform the above, it becomes possible for the hold responder to take a response according to the occurrence of the communication error.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a key telephone system of the present invention.

FIG. 2 is a flowchart showing a processing operation when a radio failure occurs in the key telephone system of FIG.

FIG. 3 is a flowchart showing a processing operation when a radio failure occurs in the button telephone system of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main device 2 Base unit 3 Slave unit 4 Telephone line 11 External line i / f circuit 12 Switch circuit 13 Extension line i / f circuit 14 Sound source 15 Control unit 21 Line i / f circuit 23 Radio circuit 25 Reception level measuring unit 26 Control unit 32 Wireless circuit 34 Control unit 37 LCD display

Claims (12)

[Claims] 1. A button telephone system that accommodates a cordless telephone as an extension telephone, and wireless communication means for relaying control data exchanged between a master and a slave of the cordless telephone via a call channel. A button comprising a holding means for putting a telephone line during a call into a system holding state when a communication error occurs in relaying the control data transmitted from the parent device to the child device by the wireless communication means. Telephone system. 2. A disconnecting means for disconnecting a wireless line between the parent and child devices in which the communication error has occurred, and a warning means for sending a warning sound to the child device before disconnecting the wireless line between the parent and child devices by the disconnecting means. 2. The button according to claim 1, further comprising: a notification unit that notifies the user of the slave unit of the disconnection of the wireless line when the disconnection unit disconnects the wireless line between the parent and child units. Telephone system. 3. The button telephone system according to claim 1, further comprising a notification unit for notifying a main device that controls the connection between the cordless telephone and an outside line when the communication error occurs. . 4. When the holding means puts a telephone line in a call into a system holding state by the holding means, an instruction means for instructing a base unit of the cordless telephone in which the communication error has occurred to connect the wireless line, and the base unit The notification means for notifying that there is an external line on hold to the cordless telephone handset in which the communication error has occurred, when the wireless line connection is successful based on the instruction of the instruction means. Button phone system. 5. The extension information indicating the occurrence of the communication error and the hold are provided to a cordless telephone in a standby state different from the cordless telephone in which the communication error has occurred, when the telephone line in the call is put into the system hold state by the holding means. 2. The button telephone system according to claim 1, further comprising a notifying unit for notifying outside line information indicating the established telephone line. 6. The child so as to perform a display in the system hold state of the telephone line during call by the holding means, which is different from the display in the system hold state of the telephone line during call due to the system hold operation from the child device. 2. The key telephone system according to claim 1, further comprising control means for controlling the machine. 7. A button telephone system accommodating a cordless telephone as an extension telephone, comprising: a measuring means for measuring a received electric field strength of an electric wave transmitted from a cordless telephone to a parent device at a constant cycle; and the measuring means. When the measurement result shows the received electric field strength below the wireless line disconnection level, the time measuring means for measuring the duration of the received electric field strength below the wireless line disconnection level, and the measurement result by the measuring means and the timing result of the time measuring means. When it is determined that the state below the wireless line disconnection level of the received electric field strength in the master unit has continued for a predetermined time, it is determined that a communication error has occurred, and a holding unit that puts the telephone line during communication into a system hold state. A button telephone system characterized in that 8. A disconnecting means for disconnecting a wireless line between the parent and child devices in which the communication error has occurred, and a warning means for sending a warning sound to the child device before disconnecting the wireless line between the parent and child devices by the disconnecting means. 8. The button according to claim 7, further comprising: a notification unit for notifying the user of the wireless unit of the disconnection of the wireless line when the wireless unit disconnects the wireless unit by the disconnecting unit. Telephone system. 9. The button telephone system according to claim 7, further comprising a notifying unit for notifying a main device that controls connection between the cordless telephone and an outside line when the communication error occurs. . 10. An instruction means for instructing a parent device of a cordless telephone in which the communication error has occurred to connect a wireless line when the holding device puts a telephone line in a call into a system on-hold state, and the parent device 8. A notification means for notifying that there is an external line on hold to the cordless telephone handset in which the communication error has occurred, when the wireless line connection is successful based on the instruction of the instruction means.
Button telephone system described. 11. The extension information indicating the occurrence of the communication error and the hold are provided to a cordless telephone in a standby state different from the cordless telephone in which the communication error has occurred, when the telephone line in the call is put into the system hold state by the holding means. 8. The button telephone system according to claim 7, further comprising a notifying unit for notifying outside line information indicating the established telephone line. 12. The child so as to perform a display in the system hold state of the telephone line during call by the holding means, which is different from the display in the system hold state of the telephone line during call by the system hold operation from the child device. 8. The key telephone system according to claim 7, further comprising control means for controlling the machine.