JP2971151B2 - Key telephone equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a key telephone device, and more particularly to a microphone (hereinafter referred to as a "phone") in addition to a handset.
A key telephone having at least one extension telephone having a microphone and a speaker, and configured to be capable of selectively setting a voice call mode using a microphone and a speaker and a call mode using a handset. Related to the device.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing an overall configuration of a key telephone apparatus conventionally used. The following description is based on the operation of each unit when the speaker of the key telephone 22 tries to make an extension call with the speaker of the key telephone 23 in the key telephone apparatus having the configuration shown in FIG. This relates to the operation of each unit when the speaker of the key telephone 22 attempts to make a local line call.

First, the operation of each unit when a speaker of the key telephone set 22 makes an extension loudspeaker call by operating a loudspeaker call mode setting means (not shown) will be considered. When the speaker of the key telephone 22 presses the extension key switch 36 while the handset is on-hook, a signal indicating that the extension key switch 36 is pressed is transmitted from the control circuit 27 to the key telephone interface unit 5, The data is supplied to the central control circuit 15 through the data highway 15b and the like. Central control circuit 1
5 receives the above signal, and transmits an LED lighting control signal and a control signal required for switching the contacts of the switching circuits 55 and 56 (hereinafter referred to as a “switching control signal”) to the control circuit 27 in the reverse direction through the above path. Send out. When the control circuit 27 receives the LED lighting control signal and the switching control signal,
The lighting control of the extension key switch LED 26 is performed. Along with this lighting control, the control circuit 27 switches the contacts of the switching circuits 55 and 56 to the terminals a and b of the loudspeaker circuit 50, respectively.

In this state, when a button on the dial pad 28 is pressed by a speaker, a dial signal by the pressing operation is given to the control circuit 27. Then, this dial signal is sent from the control circuit 27 to the central control circuit 15 through the above-mentioned path. Thus, the central control circuit 15 notifies the key telephone 23 of the incoming call.
That is, the central control circuit 15 includes the data highway 15b,
A data signal indicating that there is a call from the key telephone 22 is given to the control circuit 40 through the key telephone interface unit 6 or the like.

When receiving the data signal, the control circuit 40 controls the lighting of the extension key switch LED 39 and switches the contacts of the switching circuits 57 and 58 to the terminals a and b of the loudspeaker circuit 53, respectively. By driving the speaker 59, the speaker of the key telephone 23 is notified that the extension is being called from the key telephone 22. With this notification, when the speaker of the key telephone 23 goes off-hook on the handset and presses the extension key switch 49, a signal generated by the pressing operation is given to the control circuit 40 as a response signal to the notification. This signal is provided from the control circuit 40 to the central control circuit 15 through the above-mentioned path in the reverse direction.

When the central control circuit 15 receives the above signal, it notifies the control circuit 27 through the data highway 15b, the key telephone interface unit 5 and the like that the response signal has been transmitted from the control circuit 40 side of the key telephone 23. Give a signal. And time switch 1
4, the time slot 16a allocated on the incoming PCM highway and the time slot 19b allocated on the outgoing PCM highway, the time slot 19a allocated on the incoming PCM highway and the allocated time slot on the outgoing PCM highway. The time slot 16b is exchange-connected. As a result, the key telephone 22 and the key telephone 2
3 is in a state where extension voice communication is possible.

At the time of the above-mentioned extension call, the microphone 51
The transmission voice signal transmitted from the CDMA is subjected to signal processing as described later in the loudspeaker circuit 50, and then input to the codec 29 through the switching circuit 56 and the like.
It is converted into a CM signal. The PCM signal is transmitted from the codec 29 to the ping-pong transmission circuit 25, the key telephone interface unit 5, the time slot 16a allocated on the incoming PCM highway, etc.
4 given. The PCM signal given to the time switch 14 is given to the codec 42 through the time slot 19b allocated on the outgoing PCM highway, the key telephone interface unit 6, the ping-pong transmission circuit 38, etc., and is converted into an analog signal by the codec 42. Is done. This analog signal is output from the receiver 45 of the handset through the switching circuit 57 as received voice.

On the contrary, the transmission voice signal transmitted from the transmitter 46 of the handset is input to the codec 42 through the switching circuit 58 and the like.
Converted to a signal. This PCM signal is supplied to the time switch 14 through the ping-pong transmission circuit 38, the key telephone interface unit 6, and the like, through the time slot 19a allocated on the incoming PCM highway. The PCM signal given to the time switch 14 is
Time slot 16 allocated on CM highway
b, provided to the ping-pong transmission circuit 25 through the key telephone interface unit 5. Ping-pong transmission circuit 2
The PCM signal given to 5 is given to a codec 29, where the PCM signal is converted into an analog signal. This analog signal is output as a received voice signal from the speaker 52 through the loudspeaker circuit 50 and the like.

On the other hand, when the speaker of the key telephone 22 operates the loudspeaker communication mode setting means (not shown), etc., the operation of each unit when making a local loudspeaker communication is as follows. When the speaker of the key telephone 22 presses the central line key switch 35 while the handset is on-hook, a signal indicating that the central line key switch 35 is pressed is generated, as in the case of the extension voice call. It is provided to the central control circuit 15. Central control circuit 15
Receives the above signal, and sends the LED lighting control signal and the switching control signal of the switching circuits 55 and 56 to the control circuit 27 in the reverse direction through the above path. At the same time, the control unit 13 outputs a local line capture command signal to the control circuit 13 so as to cause the local line interface circuit 7 to perform local line capture. The central control circuit 15 controls the time switch 14 and allocates a time slot for the key telephone 22 to perform the central office public voice call. When the control circuit 27 receives the LED lighting control signal, the control circuit 27 controls the lighting of the local line key switch LED 34. In conjunction with this lighting control, the control circuit 27
The contacts 5 and 56 are switched to the terminals a and b of the loudspeaker circuit 50, respectively.

In this state, when a button on the dial pad 28 is pressed by the speaker, a dial signal by the pressing operation is given to the control circuit 27. Then, this dial signal is sent from the control circuit 27 to the central control circuit 15 through the above-mentioned path. By this dial signal, the central control circuit 15 causes the central office interface circuit 7
Then, a control signal is output to the control circuit 13 so as to transmit a dial pulse to the office line 1.

When the dial pulse output from the central office interface circuit 7 is given to the central office exchange (not shown) through the central office 1, the central office exchange (not shown) transmits the dial pulse and the corresponding terminal (not shown) corresponding to the dial pulse. To output a call signal. When the talker of this terminal goes off-hook on the handset, the central office exchange (not shown) recognizes this and sends a DC voltage signal of inverted polarity to the office in order to notify that it has been connected to the opposite terminal (not shown). Send to main unit 2 via line 1. As a result, between the key telephone 22 and the counterpart terminal (not shown), a state in which a local line loudspeaker can be performed becomes possible.

At the time of the above-mentioned central office voice call, the microphone 51
The transmission voice signal transmitted from the P.T.
It is converted into a CM signal. This PCM signal is also input to the time switch 14 along the same route as in the above-described extension voice call. The PCM signal provided to the time switch 14 is transmitted to the codec 1 through a time slot 14b allocated on the outgoing PCM highway.
2 and converted into an analog signal in the codec 12. The analog signal, that is, the transmission voice signal transmitted from the microphone 51 is transmitted to the office line 1 through the transmission amplifier 11, the 2-wire 4-wire conversion circuit 9, the communication transformer 8, and the office line interface circuit 7.

Conversely, when a dial pulse for calling the key telephone 22 is transmitted from the other party terminal (not shown) to the central office exchange (not shown), it is transmitted from the central office exchange (not shown) through the office line 1. A call signal is sent to main device 2. When the office line interface circuit 7 detects the incoming of the call signal and provides an incoming detection signal to the central control circuit 15 through the control circuit 13, the central control circuit 15
Sends a data signal to the control circuit 27 through the data highway 15b or the like to indicate that there is a call from the central office. At the same time, the central control circuit 15 controls the time switch 14 to allocate a time slot for the key telephone 22 to perform a central office public voice call. At the stage where the time slots are allocated in this way, the received voice signal transmitted from the partner terminal through the local line 1 is provided to the loudspeaker circuit 50 through the above route in the reverse direction. The received voice signal is output from the loudspeaker circuit 50 to the speaker 52, and is transmitted from the speaker 52 as a received voice.

[0014]

The central office 1 (not shown), which connects the central office exchange (not shown) and the main unit 2 of the key telephone apparatus as shown in FIG. Since the lengths of many office lines connecting many other telephones vary in length, the amount of signal transmission loss occurring in each office line naturally varies with this.
Accordingly, the level of the received voice signal from the partner terminal with which the key telephone 22 of the key telephone apparatus is performing the central office call through the central office 1 and the central office exchange (not shown) depends on the amount of transmission loss occurring in each of the central offices described above. Therefore, if the other party terminal of the local line communication is different, the value naturally becomes different.

As described above, in the case of the office line communication, the input level of the reception signal transmitted through the office line 1 varies in size. For this reason, in the conventional key telephone apparatus, a plurality of key telephones such as the key telephones 22 and 23 have loudspeaker circuits 50 and 53 in which a reception detection circuit and a transmission detection circuit as shown in FIG. (Shown in FIG. 6). Then, in consideration of the noise level around the plurality of key telephones installed, even when the input reception signal level is a small value at the time of central office loudspeaking, the transmission state is switched from the transmission state to the reception state. As described above, it is common to set the transmission state / reception state switching curve using the loudspeaker circuits 50 and 53. Note that the overall configuration of the loudspeaker circuit 50 shown in FIG. 6 and the loudspeaker circuit 50 shown in FIG. 2 described later are substantially the same. The overall structure of the reception detection circuit 50e and the transmission detection circuit 50f shown in FIG. 7 and the reception detection circuit 50e shown in FIG. 1 described later are substantially the same. Therefore, the configurations of the loudspeaker circuit 50, the reception detection circuit 50e, the transmission detection circuit 50f, and the like have been described with reference to FIGS.

By means of the loudspeaker circuit 50 (53), for example, when the noise level around the key telephone 22 (23) is indicated by a point P in FIG.
The switching curve is set on the left side of FIG. 4 as indicated by the solid lines α and β in FIG.

However, on the other hand, a ping-pong transmission system (digital transmission system) is adopted between the main unit 2 and the key telephones 22 and 23 (that is, ping-pong transmission is performed on the key telephones 22 and 23, respectively). Data transformers 24 and 37 and ping-pong transmission circuits 25 and 38 are provided, and the key telephone interface units 5 and 6 provided on the main unit 2 corresponding to the key telephones 22 and 23 respectively. The ping-pong transmission data transformers 18 and 21 and the ping-pong transmission circuits 16 and 19 are provided). In addition, the lines connecting the main unit 2 and the key telephones 22 and 23 are mostly indoor wirings, and the distance is short enough that transmission loss does not matter. Accordingly, in the extension voice call between the key telephones 22 and 23, the transmission loss of the voice signal and the like is almost zero. That is, in the extension call between the key telephones 22 and 23, the transmission and reception of the voice signal and the like are performed at a substantially constant level, and the average call level is higher than the call level in the central office call.

Therefore, as described above, the transmission state / reception state switching curve of the key telephone (22, 23, etc.)
If it is set so as to be suitable for central office loudspeaking, during internal loudspeaking, even if the input level of the received signal becomes low, it switches from the receiving state to the transmitting state immediately as in the case of central loudspeaking. However, there is a problem that the speaker gives a sense of incongruity between the public telephone call and the internal telephone call.

Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to make it possible to switch between a transmission / reception state suitable for a central loudspeaker and an extension loudspeaker. Accordingly, it is an object of the present invention to provide a key telephone apparatus which does not give a speaker a sense of incongruity between a central office call and an internal telephone call.

[0020]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a plurality of extension telephones connected to a central office,
A key telephone device comprising: a main unit for setting up an extension call for connecting and connecting the plurality of extension telephones to each other and a main unit for setting up a call for exchanging each extension telephone and the office line, wherein the plurality of extension telephones are provided. At least one of the extension telephones has a microphone and a speaker in addition to the handset, and is configured such that a loudspeaker call mode using the microphone and a speaker and a call mode using the handset can be selectively set. When the extension telephone set in the loudspeaker communication mode is performing a loudspeaker telephone call, a threshold level for switching the transmission / reception state compatible with the loudspeaker telephone call is selected. When the extension telephone set is set to, the transmission / reception state switching threshold level compatible with the extension voice call is set. A threshold level setting means for selecting, and when the extension telephone is set to a loud-speaking mode, detects a transmission signal input from the microphone and a reception signal output from the speaker, and Transmitting / receiving state determining means for determining whether the extension telephone is in a transmitting state or a receiving state from at least one of the two signals and the threshold level selected by the threshold level selecting means; The configuration was provided.

[0021]

In the above configuration, when the call mode of the extension telephone is set from the call mode using the handset to the loudspeaker call mode using the microphone and the speaker, the threshold level selecting means sets the ext. ,
It is determined which of the extension calls is being performed. If it is determined that the central office telephone call is being performed, a threshold level for transmitting / receiving state switching that is compatible with the central office telephone call of the extension telephone is selected. On the other hand, when it is determined that the extension voice call is being performed, a threshold level of the transmission / reception state switching suitable for the extension voice call of the extension telephone is selected. The threshold level selecting means outputs the threshold level selected in this way to the transmitting / receiving state determining means. When the extension telephone is set to the loudspeaker mode, the transmission / reception state determination means detects a transmission signal input from a microphone of the extension telephone and a reception signal output from a speaker of the extension telephone. Then, based on at least one of the transmission signal and the reception signal obtained by this detection and the threshold level given from the threshold level selection unit, the transmission / reception state determination unit switches the extension telephone to It is determined whether to be in the transmission state or the reception state.

In this way, when the telephone mode of the extension telephone is set from the telephone communication mode using the handset to the public telephone communication mode using the microphone and the speaker, the threshold level selecting means sets the telephone extension telephone to the local telephone public telephone communication. , Which extension extension call you are using,
Since the threshold level of the transmission / reception state switching is selected in accordance with the result of this determination, it is possible to switch the transmission / reception state suitable for the central loudspeaker and the extension loudspeaker respectively. Therefore, the speaker does not feel uncomfortable between the public telephone call and the public telephone call.

[0023]

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

FIG. 3 is a block diagram showing an overall configuration of a key telephone apparatus according to one embodiment of the present invention. FIG.
The key telephone apparatus indicated by (1) includes a plurality of key telephones having a loudspeaker circuit for controlling switching between a transmission state and a reception state in a loudspeaker mode. The configuration of the loudspeaker circuit will be described later in detail.

As is apparent from FIG. 3, the key telephone apparatus is generally composed of a main apparatus 2 and a plurality of key telephones 22 and 23 (FIG.
(Only two units are shown for convenience of illustration). The main unit 2 includes a line interface unit 3 connected to the line 1 and a key telephone 22.
, The key telephone interface unit 6 provided corresponding to the key telephone 23, and the central office interface unit 3 and the key telephone interface units 5, 6 are controlled. Central control unit 4
And The above configuration is described in more detail below.

The office line interface unit 3 is provided for connecting the office line 1 and the key telephone apparatus, and includes an office line interface circuit 7, a transformer 8, a 2-wire 4-wire conversion circuit 9, An amplifier 10, a transmission amplifier 11, a codec 12 and a control circuit 13 are provided.
The office line interface circuit 7 detects an incoming call signal from the office line, captures an office line, sends a dial pulse signal, and the like under the control of the control circuit 13. The transformer 8 is connected between the office line interface circuit 7 and the 2-wire 4-wire conversion circuit 9.

The two-wire / four-wire conversion circuit 9 receives an analog signal (received voice signal or the like) provided from the local line 1 through the local line interface circuit 7 and the transformer 8 and outputs this to the receive amplifier 10. The two-wire / four-wire conversion circuit 9 also
An analog signal (transmitted voice signal or the like) output from the transmission amplifier 11 is received and transmitted to the local line 1 through the transformer 8 and the local line interface circuit 7. The receiving amplifier 10 receives and amplifies the analog signal (received voice signal or the like) provided from the two-wire / four-wire conversion circuit 9, and outputs the amplified signal to the codec 12. On the other hand, the transmission amplifier 11 receives and amplifies an analog signal (a transmission voice signal or the like) output from the codec 12, and then outputs the amplified signal to the two-to-four-wire conversion circuit 9.

The codec 12 receives an analog signal (received voice signal or the like) amplified by the receiving amplifier 10 and digitizes the analog signal to convert it into a PCM signal. Then, this PCM signal is output to the time switch 14 constituting the central control unit 4 through the time slot 14a allocated on the incoming PCM highway. Codec 1
2 also inputs the PCM signal output from the time switch 14 through the time slot 14b allocated on the outgoing PCM highway. Then, after converting the input PCM signal into an analog signal (a transmission voice signal or the like), the PCM signal is output to the transmission amplifier 11.

The control circuit 13 is placed under the control of a central control circuit 15 constituting the central control unit 4 together with the time switch 14 described above. That is, the control circuit 13
Is connected to the central control circuit 15 through the data highway 15a.
A control signal is transmitted and received between the controller and the controller. When the control circuit 13 receives a control signal from the central control circuit 15 via the data highway 15a to capture the local line 1, the control circuit 13 controls the local line interface circuit 7 in accordance with the control signal to capture the local line 1. When the office line interface circuit 7 detects that a call signal has arrived from the office line 1, the control circuit 13 centrally controls a data signal indicating that the call signal has arrived through the data highway 15a. The signal is output to the circuit 15.

As is clear from the above description, the central control unit 4 includes a time switch 14 and a central control circuit 15.

The time switch 14 comprises a communication memory, a counter circuit and the like. And the central control circuit 15
Multiplexing, demultiplexing, or phase conversion of signals output through a plurality of incoming PCM highways under the control of, the time division switching connection between the corresponding incoming PCM highway and outgoing PCM highway is established. ing. That is, the time switch 14 receives the PCM signal given from the time slot 14a allocated on the incoming PCM highway and forms the key telephone interface unit 5 through the time slot 16b allocated on the outgoing PCM highway, for example. Output to the ping-pong transmission circuit 16. The time switch 14
Also, for example, a PCM signal output from the ping-pong transmission circuit 16 is received through the time slot 16a allocated on the incoming PCM highway, and the PCM signal is output to the codec 12 through the time slot 14b allocated on the outgoing PCM highway. It has become. The time switch 14 further constitutes the key telephone interface unit 6 with the PCM signal output from the codec 12 through the time slot 14a allocated on the incoming PCM highway and the time slot 19b allocated on the outgoing PCM highway. Ping-pong transmission circuit 19. At the same time, the time switch 14
Time slot 1 allocated on incoming PCM highway
The PCM signal output from the ping-pong transmission circuit 19 is supplied to the codec 12 through the time slot 9a and the time slot 14b allocated on the outgoing PCM highway.

Button telephone interface unit 5
Has a ping-pong transmission circuit 16, a control circuit 17, and a ping-pong transmission data transformer 18.

The ping-pong transmission circuit 16 receives a PCM signal (audio signal data) transmitted from the time switch 14 through a time slot 16b allocated on the outgoing PCM highway under the control of the control circuit 17. Then, serial digital data of the PCM signal and the control data given from the control circuit 17 is transmitted to the key telephone 22 through the ping-pong transmission data transformer 18 by the ping-pong transmission method (digital transmission method).
The ping-pong transmission circuit 16 receives serial digital data of a PCM signal (voice signal data) transmitted from the key telephone 22 by the ping-pong transmission method and control data through the ping-pong transmission data transformer 18.
The PCM signal of the serial digital data is output to the time switch 14 through the time slot 16a allocated on the incoming PCM highway, while the control data is output to the control circuit 17.

As described above, the control circuit 17 receives the control data sent from the central control circuit 15 through the data highway 15b and sends it to the ping-pong transmission circuit 16
Output to The control circuit 17 also includes the ping-pong transmission circuit 1
6 receives the control data from the key telephone set 22 and outputs it to the central control circuit 15 through the data highway 15b.

Button telephone interface unit 6
Has the same configuration as the key telephone interface unit 5.

That is, the ping-pong transmission circuit 19 receives the PCM signal (voice signal data) transmitted from the time switch 14 through the time slot 19b allocated on the outgoing PCM highway under the control of the control circuit 20. Then, serial digital data of the PCM signal and the control data given from the control circuit 20 is transmitted to the key telephone 23 through the ping-pong transmission data transformer 21 by the ping-pong transmission method. The ping-pong transmission circuit 19 receives serial digital data of a PCM signal (voice signal data) transmitted from the key telephone 23 by the ping-pong transmission method and control data through the ping-pong transmission data transformer 21. Then, the PCM signal of the serial digital data is output to the time switch 14 through the time slot 19a allocated on the incoming PCM highway.
The control data is output to the control circuit 20.

As described above, the control circuit 20 receives the control data sent from the central control circuit 15 through the data highway 15b and sends it to the ping-pong transmission circuit 19.
Output to The control circuit 20 also includes the ping-pong transmission circuit 1
9 receives the control data from the key telephone set 23 and outputs it to the central control circuit 15 through the data highway 15b.

The central control circuit 15 includes the time switch 14 described above, the various parts constituting the central line interface unit 3, and the button telephone interface units 5 and 6 (as described above, for convenience of illustration in FIG. Since only two key telephones are shown, only two key telephone interface units provided for each key telephone are shown.) Put the components that make up under its control. As described above, the central control circuit 15 controls the control circuit 1 through the data highway 15a.
3, a control signal for transmitting a line signal, a control signal for transmitting a dial pulse signal, a signal for notifying the reception of a call signal from the line 1 and the like are transmitted and received. Central control circuit 1
5 transmits the control signal through the data highway 15b to the control circuit 17 constituting the button telephone interface unit 5 together with the ping-pong transmission circuit 16 and the transformer 18 for the ping-pong transmission data. Control. In addition, the central control circuit 15 receives the control information sent from the control circuit 17 through the data highway 15b.

Similarly to the above, the central control circuit 15 sends the data highway 15b to the control circuit 20 constituting the button telephone interface unit 6 together with the ping-pong transmission circuit 19 and the ping-pong transmission data transformer 21.
The control signal is transmitted through. Thus, the central control circuit 15 not only controls the key telephone interface unit 6, but also receives control information transmitted from the control circuit 20 through the data highway 15b.

The key telephone 22 includes a ping-pong transmission data transformer 24, a ping-pong transmission circuit 25, a control circuit 27, a dial pad 28, an extension key switch 36,
Extension key switch LED 26, office line key switch 3
5. LED 34 for office line key switch, codec 29,
It includes a receiver amplifier 30, a transmitter amplifier 31, a handset receiver 32, and a band set transmitter 33. The key telephone 22 further includes a switching circuit 5 in addition to the above configuration.
5, 56, a loudspeaker circuit 50, a microphone 51, and a speaker 52
Is also provided.

Under the control of the control circuit 27, the ping-pong transmission circuit 25 converts the PCM signal (voice signal data) transmitted from the button telephone interface unit 5 through the ping-pong transmission data transformer 24 by the ping-pong transmission method with the control data. Receives serial digital data. The PCM signal of the serial digital data is output to the codec 29, while the control data is output to the control circuit 27.
The ping-pong transmission circuit 25 also receives a PCM signal (audio signal data) output from the codec 29 and control data output from the control circuit 27. And the above PC
The M signal and the control data are converted into serial digital data, and the serial digital data is output to the button telephone interface unit 5 through the ping-pong transmission data transformer 24.

The codec 29 includes a ping-pong transmission circuit 25.
Receives the PCM signal (sound signal data) output from the receiver, converts the signal into an analog signal (such as a received voice signal), and outputs the analog signal to the receiving amplifier 30. Codec 29
Further, it receives an analog signal (transmitted voice signal or the like) output from the transmitting amplifier 31, converts it into a PCM signal (voice signal data), and outputs the PCM signal to the ping-pong transmission circuit 25.

The receiving amplifier 30 receives and amplifies an analog signal (a receiving voice signal or the like) output from the codec 29. When the contact point of the switching circuit 55 is in the normal call mode in which the handset side is closed as shown in FIG.
The analog signal amplified by the receiving amplifier 30 is supplied to the handset receiver 32 through the switching circuit 55. On the other hand, when the contact point of the switching circuit 55 is in the loudspeaker communication mode in which the contact of the loudspeaker circuit 50 is closed, the analog signal amplified by the receiver amplifier 30 passes through the loudspeaker 52 through the switch circuit 55 and the loudspeaker circuit 50. Given to.

When the contact of the switching circuit 56 is in a normal call mode in which the handset side is closed as shown in FIG. 3, the transmission amplifier 31 outputs the analog signal output from the transmitter 33 of the handset through the switching circuit 56. After receiving and amplifying the transmission voice signal or the like, the signal is output to the codec 29. When the contact of the switching circuit 56 is in the loudspeaker communication mode in which the loudspeaker circuit 50 is closed, the analog signal output from the microphone 51 through the switching circuit 56 (transmitter) After receiving the audio signal and amplifying the received signal, the amplified signal is output to the codec 29.

The switching circuits 55 and 56 have their respective contacts switched based on a switching control signal output from the control circuit 27. That is, when setting the normal call mode, the contact of the switching circuit 55 closes the handset 32 side of the handset as shown in FIG.
Also closes the handset 33 side of the handset as shown. On the other hand, when setting the loudspeaker mode, the contact of the switching circuit 55 closes the terminal a of the loudspeaker circuit 50,
The contact of the switching circuit 56 closes the terminal b of the loudspeaker circuit 50.

Under the control of the control circuit 27, the loudspeaker circuit 50 controls the transmission signal input from the microphone 51, the reception signal output from the speaker 52 in the loudspeaker communication mode, and the extension loudspeaker during the office line loudspeaker communication. The key telephone 22 based on the transmission state / reception state switching curve adapted to the time of the call.
Control for switching the transmission state / reception state of

The speaker 52 outputs the analog signal output from the terminal C of the loudspeaker circuit 50 as a received voice. The micro 51 outputs the voice emitted from the speaker as an analog signal (transmitted voice signal) to the loudspeaker circuit 50 through the terminal d.

The extension key switch 36 is used for the key telephone 2
When the extension key switch 36 is pressed when the second speaker wants to make an extension call,
A signal indicating that the extension key switch 36 has been pressed is output to the control circuit 27. The extension key switch LED 26 includes an extension key switch 36
The signal indicating that the pressing operation has been performed is transmitted to the control circuit 27, the ping-pong transmission circuit 25, the ping-pong transmission data transformer 24, the ping-pong transmission data transformer 18, the ping-pong transmission circuit 16, the control circuit 17, the data The signal is supplied to the central control circuit 15 through the highway 15b, and based on this signal, a predetermined control signal is supplied from the central control circuit 15 through the above-mentioned path in the reverse direction from the control circuit 27, so that the light is turned on. .

The line key switch 35 is a key telephone 2
When the speaker 2 presses the central line key switch 35 when he / she wants to perform a local line passage (external line call), it is determined that the central line key switch 35 is pressed. The indicated signal is output from the line key switch 35 to the control circuit 27. When the central line key switch 35 is pressed, a signal indicating that the central line key switch 35 is pressed is given from the control circuit 27 to the central control circuit 15 through the above route. A predetermined control signal from the central control circuit 15 is supplied from the control circuit 27 through the above-described path in the reverse direction based on the control signal, so that the light is turned on. The dial pad 28 transmits a dial signal corresponding to a button pressed by a speaker of the key telephone 22 to the control circuit 27.

The control circuit 27 includes an extension key switch 36,
Operation information given from the office line key switch 35, the dial pad 28 and the like is input, and control data is exchanged with the central control circuit 15 through the above-described route. As a result, the control circuit 27 controls the extension key switch LED 36,
LED 34 for office line key switch, switching circuits 55 and 56,
The loudspeaker circuit 50 and the like are controlled. The switching control of the switching circuits 55 and 56 by the control circuit 27, that is, the switching setting of the talk mode of the key telephone 22 as described above is performed by the key telephone 2
This is performed based on operation information from a second call mode switching key (not shown) or a call mode switching command given from the central control circuit 15.

The key telephone 23 has the same configuration as the key telephone 22. That is, the ping-pong transmission data transformer 37, the ping-pong transmission circuit 38, and the control circuit 4
0, dial pad 41, extension key switch 49, extension key switch LED 39, office line key switch 48, office line key switch LED 47, codec 42, receiving amplifier 43, transmitting amplifier 44, handset receiver 45
And a handset transmitter 46. Like the key telephone 22, the key telephone 23 further includes switching circuits 57 and 58, a loudspeaker circuit 53, a microphone 54, and a speaker 59 in addition to the above configuration. The functions of the above components constituting the key telephone 23 are the same as those of the components constituting the key telephone 22.

Next, the operation of the above configuration will be described.
Here, the operation of each part when the speaker of the key telephone set 22 makes an extension loudspeaker call by operating the loudspeaker call mode setting means (not shown) will be considered. When the speaker of the key telephone set 22 presses the extension key switch 36 with the handset on-hook, a signal indicating that the extension key switch 36 is pressed is transmitted to the control circuit 27, the ping-pong transmission circuit 25, and the ping-pong transmission circuit. Data transformers 24, 18, ping-pong transmission circuit 1
6. The control circuit 17 is provided to the central control circuit 15 through the data highway 15b. When the central control circuit 15 receives the signal, the central control circuit 15 recognizes that the extension key switch 36 has been pressed, and transmits the LED lighting control signal and the switching control signals of the switching circuits 55 and 56 to the control circuit 27 in the reverse direction through the path. Send to. The control circuit 27 includes the LED
When the lighting control signal and the switching control signal are input, the lighting control of the extension key switch LED 26 is performed. Along with this lighting control, the control circuit 27 switches the contacts of the switching circuits 55 and 56 to the terminals a and b of the loudspeaker circuit 50, respectively.

In this state, when a button on the dial pad 28 is pressed by the speaker (ie, a specific extension number: in this case, the extension number corresponding to the key telephone 23 is dialed), A dial signal by this pressing operation is given to the control circuit 27. Then, this dial signal is sent from the control circuit 27 to the central control circuit 15 through the above-mentioned path. By this dial signal, the central control circuit 15 sends the key telephone 2 to the key telephone 2
It recognizes that call 3 is being made. Thus, the central control circuit 15 notifies the key telephone 23 of the incoming call. That is, a data signal indicating that there is a call from the key telephone 22 is given to the control circuit 40 through the data highway 15b, the control circuit 20, the ping-pong transmission circuit 19, the ping-pong transmission data transformers 21 and 37, and the ping-pong transmission circuit 38.

Upon receiving this data signal, the control circuit 40 controls the lighting of the extension key switch LED 39 and switches the contacts of the switching circuits 57 and 58 to the terminals a and b of the loudspeaker circuit 53, respectively. By driving the speaker 59, the speaker of the key telephone 23 is notified that the extension is being called from the key telephone 22. With this notification, when the speaker of the key telephone 23 goes off-hook on the handset and presses the extension key switch 49, a signal generated by the pressing operation is given to the control circuit 40 as a response signal to the notification. This signal is provided from the control circuit 40 to the central control circuit 15 through the above-mentioned path in the reverse direction.

When the central control circuit 15 receives the above signal, the central control circuit 15 sends to the control circuit 27 via the data highway 15b, the control circuit 17 and the like a signal notifying that the response signal has been sent from the control circuit 40 side of the key telephone 23. give.
By controlling the time switch 14, the time slot 16a allocated on the incoming PCM highway and the outgoing PCM are controlled.
A time slot 19b allocated on the M highway,
Time slot 1 allocated on incoming PCM highway
9a and the time slot 16b allocated on the outgoing PCM highway are exchanged. As a result, the extension telephone conversation between the key telephone 22 and the key telephone 23 becomes possible.

At the time of the above extension call, the microphone 51
Is transmitted to the loudspeaker circuit 50 through the terminal d. This transmission voice signal is transmitted to a loudspeaker circuit 5.
0, after signal processing as described later is performed,
Codec 29 through switching circuit 56 and transmission amplifier 31
And converted into a PCM signal by the codec 29. The PCM signal is transmitted from the codec 29 to the ping-pong transmission circuit 25, the ping-pong transmission data transformer 24,
8. The ping-pong transmission circuit 16 is provided to the time switch 14 through a time slot 16a allocated on the incoming PCM highway. The PCM signal supplied to the time switch 14 is supplied to a codec 42 through a time slot 19b allocated on the outgoing PCM highway, a ping-pong transmission circuit 19, ping-pong transmission data transformers 21 and 37, and a ping-pong transmission circuit 38. At 42, it is converted to an analog signal. This analog signal is output from the receiver 45 of the handset through the receiving amplifier 43 and the switching circuit 57 as a receiving voice signal.

Conversely, the transmission voice signal transmitted from the transmitter 46 of the handset is input to the codec 42 through the switching circuit 58 and the transmission amplifier 44, and is converted into a PCM signal by the codec 42. This PCM signal is
The signal is supplied to the time switch 14 through the ping-pong transmission circuit 38, the key telephone interface unit 6, and the like through the time slot 19a allocated on the incoming PCM highway. The PC given to the time switch 14
The M signal is provided to the ping-pong transmission circuit 25 through the time slot 16b allocated on the outgoing PCM highway and the key telephone interface unit 5. The PCM signal supplied to the ping-pong transmission circuit 25 is supplied to a codec 29, where the PCM signal is converted into an analog signal. This analog signal is received by the receiver amplifier 30,
The received voice is output from the speaker 52 through the switching circuit 55 and the loudspeaker circuit 50.

On the other hand, when the speaker of the key telephone 22 operates the loudspeaker communication mode setting means (not shown) or the like, the operation of each unit when making the loudspeaker communication at the local line is as follows. When the speaker of the key telephone 22 presses the central line key switch 35 while the handset is on-hook, a signal indicating that the central line key switch 35 is pressed is transmitted to the control circuit 27, the ping-pong transmission circuit 25, and the like. 16, and provided to the central control circuit 15 through the data highway 15b and the like. When the central control circuit 15 receives the above signal, the central control circuit 15 recognizes that the local line key switch 35 has been pressed, and the LED lighting control signal and the switching circuit 5
The switching control signals 5 and 56 are transmitted to the control circuit 27 in the reverse direction through the above path. At the same time, the control circuit 1 controls the station line interface circuit 7 to perform station line acquisition.
3 and outputs a local line capture command signal. The central control circuit 15 performs the above-described control and controls the time switch 1
4 allows the key telephone 22 to allocate a time slot for performing a line loudspeaker path (reference numeral 14).
a, 14b, 16a, 16b). When the control circuit 27 receives the LED lighting control signal, the control circuit 27 controls the lighting of the local line key switch LED 34. Along with this lighting control, the control circuit 27 switches the contacts of the switching circuits 55 and 56 to the terminals a and b of the loudspeaker circuit 50, respectively.

In this state, when a button on the dial pad 28 is pressed by the speaker (ie, when an arbitrary office line number is dialed), a dial signal by this pressing operation is given to the control circuit 27. Then, this dial signal is sent from the control circuit 27 to the central control circuit 15 through the above-mentioned path. By this dial signal, the central control circuit 15 sends the office line 1 to the office line interface circuit 7.
Control circuit 1 for transmitting dial pulses to the
3 to output a control signal.

When the dial pulse output from the office line interface circuit 7 is given to the central office exchange (not shown) through the office line 1, the central office exchange (not shown) transmits the dial pulse and the corresponding terminal (not shown) corresponding to the dial pulse. To output a call signal. When the talker of this terminal goes off-hook on the handset, the central office exchange (not shown) recognizes this and sends a DC voltage signal of inverted polarity to the office in order to notify that it has been connected to the opposite terminal (not shown). Send to main unit 2 via line 1. As a result, between the key telephone 22 and the counterpart terminal (not shown), a state in which a local line loudspeaker can be performed becomes possible.

At the time of the above-mentioned central office telephone call, the microphone 51
The transmission voice signal transmitted from the P.T.
It is converted into a CM signal. This PCM signal is also input to the time switch 14 along the same route as in the above-described extension voice call. The PCM signal provided to the time switch 14 is transmitted to the codec 1 through a time slot 14b allocated on the outgoing PCM highway.
2 and converted into an analog signal in the codec 12. This analog signal, that is, the transmission voice signal transmitted from the microphone 51 is transmitted to the office line 1 through the transmission amplifier 11, the 2-wire 4-wire conversion circuit 9, the communication transformer 8, and the office line interface circuit 7.

Conversely, when a dial pulse for calling the key telephone 22 is transmitted from the partner terminal (not shown) to the central office exchange (not shown), the central office exchange (not shown) passes through the office line 1. A call signal is sent to main device 2. When the office line interface circuit 7 detects the incoming of the call signal and provides an incoming detection signal to the central control circuit 15 through the control circuit 13, the central control circuit 15
Sends a data signal to the control circuit 27 to the control circuit 27 through the data highway 15b, the control circuit 17, and the like, indicating that there is a call from the central office. At the same time, the central control circuit 15 controls the time switch 14 to allocate a time slot for the key telephone 22 to perform the central office public voice call (reference numerals 14a, 14b, 16a, and 16a).
16b). At the stage where the time slots are allocated in this way, the received voice signal transmitted from the partner terminal through the local line 1 is provided to the loudspeaker circuit 50 through the above route in the reverse direction. The received voice signal is output from the loudspeaker circuit 50 to the speaker 52 through the terminal C, and transmitted from the speaker 52 as a received voice.

FIG. 2 is a block diagram showing an internal configuration of a loudspeaker circuit 50 according to an embodiment of the present invention. FIG. 1 shows an internal configuration of a reception detection circuit 50e incorporated in the loudspeaker circuit 50. FIG. The loudspeaker circuit 50 shown in FIG. 2 is provided in the key telephone 22 according to one embodiment of the present invention. The internal configuration of the loudspeaker circuit 50 is the same as that of the key telephone 23 shown in FIG. This is the same as the internal configuration of the loudspeaker circuit 53. The internal configuration of the reception detection circuit 50e shown in FIG. 1 is the same as the internal configuration of the reception detection circuit (not shown) incorporated in the loudspeaker circuit 53. Therefore, the illustration and description of the internal configuration of the loudspeaker circuit 53 on the key telephone set 23 side and the illustration and description of the internal configuration of the reception detection circuit (not shown) incorporated in the loudspeaker circuit 53 are omitted.

In FIG. 2, the microphone side amplifier 50a is
The transmission signal input from the microphone 51 through the terminal d is amplified, and the amplified transmission signal is transmitted to the transmission amplification amount increasing / decreasing circuit 5.
0c and the transmission detection circuit 50f. In the transmission amplification amount increasing / decreasing circuit 50c, the loss amount (the reverse of the amplification amount) is controlled by the control signal output from the comparison circuit 50g. The transmission signal output from the microphone-side amplifier 50a is input to a transmission amplification amount increasing / decreasing circuit 50c whose loss amount is controlled as described above, and is transmitted from the transmission amplification amount increasing / decreasing circuit 50c through a terminal b. It is output to the outside of 50. The transmission signal output from the loudspeaker circuit 50 is
The signal is supplied to the transmission amplifier 31 through the switching circuit 56 shown in FIG.

In the reception amplification amount increasing / decreasing circuit 50d, similarly to the transmission amplification amount increasing / decreasing circuit 50c, the loss amount is controlled by the control signal output from the comparison circuit 50g. From the switching circuit 55 shown in FIG.
The received signal input through the receiver-amplified amount increasing / decreasing circuit 50d whose loss amount is controlled as described above is input to the speaker-side amplifier 5d.
0b and the reception detection circuit 50e. The reception signal input to the speaker-side amplifier 50b is amplified by the speaker-side amplifier 50b and then output to the speaker 52 through the terminal C.

The transmission detection circuit 50f is a conventional loudspeaker circuit 5.
0 has a circuit configuration similar to that of the reception detection circuit 50e (shown in FIG. 6) incorporated therein. That is, the transmission detection circuit 50f includes a non-inverted ideal diode and an integration circuit. This non-inverting ideal diode is shown in FIG.
As shown by the operational amplifier A _1, the operational amplifier A diode D ₁ connected to the output side of the _1, the operational amplifier A ₁
, A diode D ₂ connected between the output of the operational amplifier A _{1 and} an inverting input of the operational amplifier A ₁ , a resistor R ₁ connected between the inverting input and the ground, and an output of the operational amplifier A _1. and a resistor R ₂ connected between the inverting input of the operational amplifier a _1. That is, the input voltage to the non-inverting ideal diode is applied between the reference potential (ground) and the non-inverting input terminal of the operational amplifier A _1. On the other hand, to the inverting input terminal of the operational amplifier A _1, the voltage obtained by dividing the output voltage of the operational amplifier A ₁ by the resistors R ₁ and R ₂ is adapted to be negative feedback. The gain of this non-inverting ideal diode is 1+ (R ₂ /
R ₁ ).

On the other hand, as shown in FIG.
A resistor R ₃ connected to the output side of the non-inverting ideal diode described above, it consists of a capacitor C connected between the resistor R ₃ and the ground.

If the voltage signal applied to the non-inverting input terminal of the operational amplifier A ₁ is positive, the diode D ₁ becomes conductive and the diode D ₂ becomes non-conductive, so that the input voltage signal becomes 1+ (R ₂ / R ₁ ), and is output to the integration circuit after multiplication. The output voltage signal from the non-inverting ideal diode is integratedly charged in the capacitor C by a time constant R ₃ C determined by the value of the resistor R _{3 and} the value of the capacitor C. On the other hand, contrary to the above, if the voltage signal applied to the non-inverting input terminal of the operational amplifier A ₁ is negative, diode D
_{Since 1} is non-conductive and the diode D ₂ is conductive, the charge integrated in the capacitor C is discharged from the capacitor C through the resistors R ₃ , R ₂ and R ₁ . In other words, if taking increase the time constant of the integration circuit determined by the resistor R ₃ and capacitor C, the output signal from the transmitting detection circuit 50f becomes possible which is equivalently the full-wave rectification. The output signal from the transmission detection circuit 50f is provided to a comparison circuit 50g.

In this embodiment, the reception detection circuit 50e has a circuit configuration as shown in FIG. That is, the reception detection circuit 50e according to the present embodiment is also the transmission detection circuit 50e.
Like f, it is constituted by a non-inverting ideal diode and an integrating circuit. This non-inverting ideal diode is shown in FIG.
As shown by the operational amplifier A _1, the operational amplifier Taiodo D ₁ which is connected to the output side of the A _1, an operational amplifier A ₁
The output-side operational amplifier A ₁ at the inverting input side a diode D ₂ which is connected between, between the output of the operational amplifier A ₁ and the inverting input of the operational amplifier A _1, the diode D
And a resistor R ₂ connected to ₂ to become parallel. The non-inverting ideal diode further includes, in addition to the above configuration, a resistor R ₁ having one end grounded,
₁ and the resistance R ₄ of the resistance value is different from the resistor R ₁ which is grounded similarly one end, in accordance with switching control signal supplied through the terminal e of the public address circuit 50 from the control circuit 27,
A switching circuit 60 for selectively connecting either _{one of} the resistors R ₁ and R ₄ and the inverting input side of the operational amplifier A ₁ is provided. In the following description, the value of the resistor R ₄ is
Assume it is greater than ₁ .

[0070] Input voltage to the noninverting ideal diode is applied between the reference potential (ground) and the non-inverting input terminal of the operational amplifier A _1. On the other hand, different voltages are applied to the inverting input terminal of the operational amplifier A ₁ when the switching circuit 60 is connected to the resistor R ₁ and when the switching circuit 60 is connected to the resistor R _4. Applied. That is, the switching circuit 60
There When connecting the resistor R ₁ side, the operational amplifier A
Voltage obtained by dividing _one of the output voltage by the resistors R ₁ and R ₂ is adapted to be negative feedback. Further, when the switching circuit 60 is connected to resistor R ₄ side, a voltage obtained by dividing the output voltage of the operational amplifier A ₁ by a resistor R ₄ and the resistor R ₂ is adapted to be negatively fed back . The switching circuit 60 has a resistor R ₁
When connecting a side, the gain of the noninverting ideal diode is determined by _{1 + (R 2 / R 1} ). On the other hand, when the switching circuit 60 is connected to resistor R ₄ side,
The gain of this non-inverting ideal diode is 1+ (R ₂ /
R ₄ ).

As shown in FIG. 1, the integrating circuit includes a resistor R ₃ connected to the output side of the above-mentioned non-inverting ideal diode, and a capacitor C connected between the resistor R ₃ and the ground. And consists of (A) If the switching circuit 60 is connected to resistor R ₁ side.
This indicates a state in which the control circuit 27 sets the key telephone 22 in the central office telephone call mode. More specifically, it is shown that the transmission state / reception state switching curve of the key telephone 22 is set to the solid line α and the solid line β in FIG.

If the voltage signal applied to the non-inverting input terminal of the operational amplifier A ₁ is positive, the diode D ₁ becomes conductive and the diode D ₂ becomes non-conductive, so that the input voltage signal becomes 1+ (R ₂ + R ₁ ) After being amplified twice, it is output to the integration circuit. The output voltage signal from the non-inverting ideal diode is integratedly charged in the capacitor C by a time constant R ₃ C determined by the value of the resistor R _{3 and} the value of the capacitor C. On the other hand, contrary to the above, if the voltage signal applied to the non-inverting input terminal of the operational amplifier A ₁ is negative, diode D
_{Since 1} is non-conductive and the diode D ₂ is conductive, the charge integrated in the capacitor C is discharged from the capacitor C through the resistors R ₃ , R ₂ and R ₁ . (B) if the switching circuit 60 is connected to resistor R ₄ side.
This shows a state in which the control circuit 27 sets the key telephone 22 in the extension voice communication mode. As described above, since R ₁ <R ₄ , in this state, the gain of the reception detection circuit 50e becomes smaller than the gain of the reception detection circuit 50e at the time of local line loudspeaking. The / receipt state switching curve moves from the solid line α and the solid line β in FIG. 4 to the broken line α ′ and the broken line β ′, respectively. That is, the level of the output signal from the reception detection circuit 50e decreases by an amount corresponding to the decrease in the gain of the reception detection circuit 50e as described above, and a signal having a level corresponding to the decrease in the gain is input. Unless it is performed, switching between the transmission state and the reception state of the key telephone 22 does not occur. In this manner, the transmission state / reception state switching curve shifts from the solid line α and the solid line β in FIG. And the broken line β '.

In this case as well, if the voltage signal applied to the non-inverting input terminal of the operational amplifier A ₁ is positive, the diode D ₁ becomes conductive and the diode D ₂ becomes non-conductive. Is amplified by 1+ (R ₂ / R ₄ ) and then output to the integration circuit. The output voltage signal from the non-inverting ideal diode is integratedly charged in the capacitor C by a time constant R ₃ C determined by the value of the resistor R _{3 and} the value of the capacitor C. On the other hand, if the voltage signal applied to the non-inverting input terminal of the operational amplifier A ₁ is negative, the diode D ₁ becomes non-conductive and the diode D ₂ becomes conductive. The electrically charged charge is transferred from the capacitor C to the resistors R ₃ , R ₂ ,
And thus it is discharged through the resistor R _1.

In each of the cases (a) and (b), if the time constant of the integrating circuit determined by the resistor R ₃ and the capacitor C is set large, the output signal from the reception detecting circuit 50e is equivalent. The full-wave rectification is performed. The output signal from the reception detection circuit 50e is provided to a comparison circuit 50g.

The comparison circuit 50g compares the output from the transmission detection circuit 50f with the output from the reception detection circuit 50e, and according to the comparison result, the transmission amplification amount increasing / decreasing circuit 50c or the reception amplification amount increasing / decreasing circuit 50d. , A reciprocal control is performed on the transmission amplification amount increase / decrease circuit 50c and the reception amplification amount increase / decrease circuit 50d. That is, the transmission detection circuit 50
When the level of the output signal from f is higher than the level of the output signal from the reception detection circuit 50e, the loss of the transmission amplification amount increasing / decreasing circuit 50c is eliminated, and the reception amplification amount increasing / decreasing circuit 5c is eliminated.
Control is performed to add a loss to 0d. Then, the key telephone 22 is set to the transmission state. On the other hand, when the level of the output signal from the reception detection circuit 50e is higher than the level of the output signal from the transmission detection circuit 50f, the loss of the reception amplification amount increase / decrease circuit 50d is eliminated, and the transmission amplification amount increase / decrease circuit 50c
To control the loss. And key telephone 2
2 is in the receiving state.

Next, when the key telephone 22 is set to the central office loudspeaker mode, the transmission / reception state switching control of the key telephone 22 and the key telephone 22 are set to the extension loudspeaker mode. Key telephone 2
The transmission / reception state switching control of No. 2 will be described. (C) A case where the key telephone 22 is set to the central office telephone call mode by the control circuit 27. Key telephone 22
Is set to the local line loudspeaker mode, the transmission state / reception state switching curve is represented by the solid line α and the solid line β in FIG.
Is set to

Now, it is assumed that a transmission signal is input to the loudspeaker circuit 50 in a state where no reception signal is input. This state is indicated by a point p in FIG. If only the transmission signal is input, the output signal from the transmission detection circuit 50f is naturally larger than the output signal from the reception detection circuit 50e. Therefore, the comparison circuit 50g performs the control described above. With this, the key telephone 22 is set to the transmission state. From this state, the input level of the reception signal gradually increases, whereby the output signal from the reception detection circuit 50e increases beyond the loss amount of the reception amplification amount increasing / decreasing circuit 50d, and the level of the output signal from the transmission detection circuit 50f. (Point Q in FIG. 4, this point Q exists on the solid line α)
Is exceeded, the comparison circuit 50g outputs the reception amplification amount increase / decrease circuit 5
Control is performed to eliminate the loss of 0d and to add a loss to the transmission amplification amount increase / decrease circuit 50c. With this control, the key telephone 2 switches from the transmitting state to the receiving state.

In the key telephone 22 controlled to be in the receiving state as described above, the input level of the receiving signal gradually decreases, so that the output signal from the receiving detecting circuit 50e becomes equal to or less than the loss amount of the receiving amplification increasing / decreasing circuit 50d. When the output signal level from the transmission detection circuit 50f falls below the level (point R in FIG. 4, this point R exists on the solid line β), the comparison circuit 50g again operates the transmission amplification amount increasing / decreasing circuit 50.
Control is performed to eliminate the loss of c and add a loss to the reception amplification amount increasing / decreasing circuit 50d. With this control, the key telephone 2
2 switches from the receiving state to the transmitting state.

As is clear from the above description, the switching from the transmitting state to the receiving state of the key telephone 22 is performed at the level of the solid line α, and the switching from the receiving state to the transmitting state is performed by the solid line. Performed at the level of β. In FIG. 4, the sign x _dB indicating the difference between the solid line α and the solid line β is
It shows the maximum value of the loss amount in the reception amplification amount increasing / decreasing circuit 50d. (D) The case where the key telephone 22 is set to the extension voice communication mode by the control circuit 27. Key telephone 22
Is set to the extension voice communication mode, the transmission state / reception state switching curve is set to the dashed lines α ′ and β ′ in FIG. It is assumed that a transmission signal is input in a state where no reception signal is input to the loudspeaker circuit 50.
This state is indicated by a point P in FIG. If only the transmission signal is input, the output signal from the transmission detection circuit 50f is naturally larger than the output signal from the reception detection circuit 50e. Therefore, the comparison circuit 50g includes the transmission amplification amount increasing / decreasing circuit 50c. Of the receiver, the receiving amplification amount increasing / decreasing circuit 50d
The key telephone 22 is set to the transmitting state by performing control to add a loss to the key telephone. From this state, the input level of the reception signal gradually increases, and as a result, the reception detection circuit 5
0e becomes larger than the loss amount of the reception amplification amount increasing / decreasing circuit 50d, and the level of the output signal from the transmission detection circuit 50f (point Q 'in FIG. 4, this point Q' Exceeds), the comparison circuit 50g
Performs control to eliminate the loss of the reception amplification amount increasing / decreasing circuit 50d and to add the loss to the transmission amplification amount increasing / decreasing circuit 50c. With this control, the key telephone 22 switches from the transmitting state to the receiving state.

In the key telephone 22 controlled to the receiving state as described above, the input level of the receiving signal is gradually reduced, so that the output signal from the receiving detecting circuit 50e becomes equal to or less than the loss amount of the receiving amplifying circuit 50d. When the level of the output signal from the transmission detection circuit 50f falls below the level (point R 'in FIG. 4, this point R' exists on the solid line β '), the comparison circuit 50g again operates the transmission amplification amount increasing / decreasing circuit. Control is performed to eliminate the loss of 50c and to introduce the loss of the reception amplification amount increasing / decreasing circuit 50d. With this control, the key telephone 22 switches from the receiving state to the transmitting state.

As is apparent from the above description, the switching of the key telephone 22 from the transmission state to the reception state is performed by the broken line α '.
The switching from the receiving state to the transmitting state is performed at the level indicated by the broken line β '.
In FIG. 4, the sign x _dB indicating the difference value between the broken line α 'and the broken line β' indicates the maximum value of the loss amount in the reception amplification amount increasing / decreasing circuit 50d, as described above.

As described above, according to the key telephone apparatus according to the embodiment of the present invention, when the call mode of the key telephone 22 is set to the loudspeaker call mode by the control circuit 27, the control circuit 27 Telephone 22
Is determined to be making a public address call,
Connect the switching circuit 60 to the resistor R ₁ side receiving detection circuit 22
4, the solid line α and the solid line β
The transmission / reception switching characteristics suitable for the central office public voice call are indicated as shown in FIG.
When 2 is determined to perform the extension loudspeaker call, by reducing the gain of the receiving detection circuit 22 connects the switching circuit 60 to the resistor R ₄ side, FIG. 4, dashed alpha, the dashed line β As shown in the figure, the transmission / reception switching characteristics suitable for the extension voice call are used, and the comparison circuit 50g determines the transmission / reception switching characteristics, the transmission detection signal and the reception detection signal from the transmission / reception switching signal and the reception voice detection signal. Since the switching control of transmission / reception is performed at different times, it is possible to provide a key telephone apparatus that does not give a speaker a sense of incompatibility.

In the key telephone apparatus according to the present embodiment, the control circuit 27 adjusts the gain of the reception detection circuit 50e in the manner described above, but the transmission detection circuit 50f is used instead of the reception detection circuit 50e. The gain of the reception detection circuit 50e and the gain of the transmission detection circuit 50f may be adjusted.
The loudspeaker circuit 50 (53) may be configured.

[0084]

As described above, according to the present invention,
At least one of the plurality of extension telephones has a microphone and a speaker in addition to the handset, and is configured to be capable of selectively setting a voice call mode using the microphone and the speaker and a call mode using the handset. When the extension telephone set in the loudspeaker communication mode is performing a central office loudspeaker call, the extension telephone has a threshold level for transmission / reception state switching compatible with the central office loudspeaker communication. A threshold level selecting means for selecting a threshold level of transmission / reception state switching compatible with the extension voice call when the selected extension telephone set is in the voice call mode and performing the extension voice call. And a transmission signal input from the microphone and an output from the speaker when the extension telephone is set to a loudspeaker mode. And the threshold level selected by the threshold level selection means is used to determine whether the extension telephone is to be in the transmission state or the reception state. Since the transmission / reception state determination means for determining the transmission / reception state determination means is provided, it is possible to set the transmission state / reception state switching curve suitable for the office line extension call and the extension line speech, respectively. It is possible to provide a key telephone device that does not give a speaker a sense of incompatibility between a line loudspeaker call and an extension loudspeaker call.

[Brief description of the drawings]

FIG. 1 is a diagram showing an internal configuration of a reception detection circuit provided in a loudspeaker circuit according to one embodiment of the present invention.

FIG. 2 is a diagram showing an internal configuration of a loudspeaker circuit provided in the key telephone according to one embodiment of the present invention.

FIG. 3 is a block diagram showing an overall configuration of the key telephone apparatus according to one embodiment of the present invention.

FIG. 4 is a diagram showing transmission / reception switching characteristics at the time of local line loudspeaking and transmission / reception switching characteristics at the time of extension loudspeaking when the key telephone set according to one embodiment of the present invention is set to the loudspeaker communication mode. FIG.

FIG. 5 is a block diagram showing an overall configuration of a key telephone device according to the related art.

FIG. 6 is a diagram showing an internal configuration of a loudspeaker circuit provided in a key telephone according to the related art.

FIG. 7 is a diagram showing an internal configuration of a reception detection circuit and a transmission detection circuit provided in a conventional loudspeaker circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 office line 2 main unit 22 key telephone 23 key telephone 27 control circuit 32 transmitter 33 receiver 40 control circuit 45 transmitter 46 receiver 50 loudspeaker circuit 50 c transmission amplification increase / decrease circuit 50 d reception amplification increase / decrease circuit 50 e reception detection circuit 50f Transmission detection circuit 50g Comparison circuit 51 Microphone 52 Speaker 54 Microphone 59 Speaker 60 Switching circuit

Claims (1)

(57) [Claims] A plurality of extension telephones connected to a central office,
A key telephone device comprising: an extension call for exchanging and connecting the plurality of extension telephones with each other; and a main device for setting an extension call for exchanging and connecting each of the extension telephones to the office line, wherein the plurality of extension telephones are provided. At least one of the extension telephones has a microphone and a speaker in addition to the handset, and is configured such that a loudspeaker call mode using the microphone and the speaker and a call mode using the handset can be selectively set. When the extension telephone set to the loudspeaker communication mode is performing a loudspeaker communication, a threshold level for switching the transmission / reception state compatible with the loudspeaker communication is selected. When the extension telephone set is set to, the transmission / reception state switching threshold level compatible with the extension voice call is set. A threshold level selecting means for selecting, and when the extension telephone is set to the loud-speaking mode, detects a transmission signal input from the microphone and a reception signal output from the speaker, and Transmitting / receiving state determining means for determining whether the extension telephone is in a transmitting state or a receiving state from at least one of the two signals and the threshold level selected by the threshold level selecting means; A key telephone device, which is provided.