JPH071640U - Telephone device with howling prevention function - Google Patents

Abstract

(57) [Abstract] [Purpose] A phone with a howling prevention function that prevents the generation of howling noise and improves service by maintaining the impedance balanced state for a certain period of time at the end of a call when the impedance balance of the call loop is disrupted. Provide a device. A key telephone 1 and an intercom 2 having an extension function are connected to each other via extensions 3-1, 3-2, 4-1 and 4-2, and call-end detection circuits 15a and 15b and an impedance circuit 12a are provided respectively. , 12b are provided. When the key telephone 1 hangs up first, the impedance circuit 12a is connected in parallel to the extension lines 3-1 and 3-2 for a predetermined time after the end of the call,
The impedance balance state is maintained at least until the end processing is completed on the doorphone side.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a telephone device with a howling prevention function, which is used for extension calls between a plurality of telephones having extension functions, such as intercom calls between button telephones and doorphones, simple extension handsfree calls between button telephones, etc. It is a thing.

[0002]

[Prior art]

 As a conventional example of a telephone system used for an extension call between a plurality of telephones having extension functions, for example, a doorphone call between a button telephone and an intercom, or an extension simple hands-free call between a button telephone and an extension telephone, for example, There is one shown in 4. In FIG. 4, 51 and 52 are various telephones having an extension function such as a button telephone and an intercom. Here, the following explanation is given assuming that the telephone 51 is a button telephone and the telephone 52 is an intercom. expand.

The key telephone 51 and the doorphone 52 are connected to the call circuits 55 and 56 via extension lines 53-1 and 53-2 and extension lines 54-1 and 54-2, respectively. The key telephone 51 connects one end of the telephone network 58a to the extension 53-1 via the hook switch 57a, and connects the other end of the telephone network 58a to the extension 53-2 together with one end of the transmission / reception amplifier 59a. The other end of the reception amplifier 59a is connected to the extension line 53-1 and the speaker 60a and the microphone 61a are connected to the output side of the transmission / reception amplifier 59a. Similarly, the intercom 52 connects one end of the telephone network 58b to the extension 54-1 via the hook switch 57b, and connects the other end of the telephone network 58b to the extension 54-2 together with one end of the transmission / reception amplifier 59b. The other end of the transmission / reception amplifier 59b is connected to the extension 54-1 and the speaker 60b and the microphone 61b are connected to the output side of the transmission / reception amplifier 59b.

The call circuits 55 and 56 have call current supply circuits 62a and 62b connected to the extension lines 53-1 and 53-2 and the extension lines 54-1 and 54-2, respectively. -1, 53-2 and extension lines 54-1 and 54-2 are always connected in parallel to the dummy circuits 63a and 63b, respectively. Since the call circuits 55 and 56 are normally housed in one main device as shown by the dotted line in the figure, the call current supply circuits 62a and 62b are often integrated in the main device.

[0005]

[Problems to be solved by the device]

 In such a conventional telephone system, in general, impedance is balanced in the same call loop during mutual call (for example, during a phone call), so at the end of the call (end of call). When the calling party (eg, the party of the key telephone 51) hangs the handset on the hook switch 57a, the extension 53-1 is opened and the impedance balance of the entire calling system is lost. At the same time, the call-end side (doorphone 52 side) issues a call termination command, but there is a time lag before the call termination processing is performed based on the call termination processing command. Since the supply circuit 62b is alive, the called party hears the howling sound generated from the speaker 60b with a built-in intercom (when the mutual call is an extension simple hands-free call, similarly, (You will hear a howling sound generated from the speaker of the telephone on the calling side), which is not desirable for service. Therefore, in order to prevent this howling, a dummy circuit is always connected to the speech path as shown in FIG. 4, but in that case, a voice signal loss on the speech path is caused.

In the present invention, when a situation occurs where the impedance balance of the call loop is lost, the howling noise is prevented by maintaining the impedance balance state for a certain period of time to improve the service. The purpose is to provide a telephone device with a built-in telephone.

[0007]

[Means for Solving the Problems]

 To this end, the present invention provides a telephone device in which a plurality of telephones having an extension function are interconnected via an extension communication path, and each of the telephones is provided with an end-of-call detection circuit and an impedance circuit, and the end-of-line detection It is characterized in that the impedance circuit on the telephone side where the call is made is connected in parallel to the extension communication path for a predetermined time after the end of the call.

[0008]

[Action]

 According to the present invention, at the end of a mutual call between a plurality of telephones having an extension function, which are interconnected via an extension call path, the call loop is opened and the impedance balance is about to be lost. The end-of-call detection circuit detects the end-of-call, and based on the detection of the end-of-call, the impedance circuit on the telephone side that ended the call is connected in parallel to the extension communication path for a predetermined time after the end of the call. The impedance balance of the call loop is maintained until the call termination processing is completed on the telephone side in the call state. As a result, howling is prevented and service is improved.

[0009]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing in principle the system configuration of a telephone device with a howling prevention function according to the present invention. This system is applied to extension calls between a plurality of telephones having extension functions, such as doorphone calls between button telephones and doorphones, simple extension hands-free calls between button telephones, etc. The following explanation is developed assuming that 1 is a key telephone and telephone 2 is an intercom. It should be noted that a system having three or more telephones having an extension function can of course be configured, but in that case, the principle is the same as the case of having two telephones having an extension function.

In FIG. 1, a key telephone 1 and an intercom 2 are connected to communication circuits 5 and 6 via extensions 3-1 and 3-2 and extensions 4-1 and 4-2, respectively. The key telephone 1 connects one end of the telephone network 8a to the extension 3-1 via the hook switch 7a, and connects the other end of the telephone network 8a to the extension 3-2 together with one end of the transmission / reception amplifier 9a. The other end of the reception amplifier 9a is connected to the extension 3-1 and the speaker 10a and the microphone 11a are connected to the output side of the transmission / reception amplifier 9a. Similarly, the intercom 2 connects one end of the telephone network 8b to the extension 4-1 via the hook switch 7b, and connects the other end of the telephone network 8b to the extension 4-2 together with one end of the transmission / reception amplifier 9b. The other end of the transmission / reception amplifier 9b is connected to the extension line 4-1, and the speaker 10b and the microphone 11b are connected to the output side of the transmission / reception amplifier 9b.

The call circuits 5 and 6 are call-end impedance circuits 12a and 12b and call-end impedance circuits 12a and 12b connected to the extension lines 3-1 and 3-2 and the extension lines 4-1 and 4-2, respectively. Has speech current supply circuits 14a and 14b connected via the wiring 13a and the extension line 3-2 and the wiring 13b and the extension line 4-2, respectively, and the end-of-call impedance circuits 12a and 12b respectively detect the end of call. The circuits 15a and 15b are incorporated. Since the call circuits 5 and 6 are normally housed in one main device as shown by the dotted line in the figure, the call current supply circuits 14a and 14b are often integrated in the main device. .

FIG. 2 is a circuit diagram illustrating a specific configuration of the impedance circuit 12a (12b) at the end of call. In FIG. 2, the collector of the transistor TR1 is connected to the wiring 13a (13b) via the resistor R1, and the wiring 13a (13b) is connected to the extension line 3-1 (4-1) via the diode portion of the photocoupler PC 1. To be done. The base of the transistor TR1 is connected to the resistors R2 and R3, and the emitter of the transistor TR1 and the other end of the resistor R2 are connected to the extension line 3-2 (4-2). A capacitor C1 and a diode D1 having the other end connected to an extension line 3-2 (4-2) are connected to the other end of the resistor R3. The other end of the capacitor C1 is connected to the collector of the photocoupler PC1 together with the resistors R4 and R5. The other end of the resistor R4 is connected to the wiring 13a (13b), and the other end of the resistor R5 is connected to the extension line 3-2 (4-2) together with the emitter of the photocoupler PC1.

Next, the operation of this embodiment will be described based on the timing chart of FIG. In the present embodiment, the following description is developed assuming that the calling side telephone is the button telephone 1 and the called side telephone is the doorphone 2 (in the case of simple extension handsfree extension telephone call). , The explanation is omitted because the intercom 2 should be read as the button telephone 2.

First, when the calling party lifts the handset in response to a call from the intercom 2 (handset OFF HOOK), the call current supply circuit 14a and the photocoupler PC1 are turned on, and the transistor TR1 is turned off. , Button phone 1 is ready to talk. At this time, the called party remains in the standby state. Thereafter, when the calling party dials a predetermined destination number (in this case, the intercom number), the call current supply circuit 14b, the speaker 10b, and the microphone 11b of the called intercom 2 after a predetermined time has elapsed. Is turned on, and mutual extension calls become possible, so the extension call is started in response to the response from the called party.

When the extension call ends, for example, by the caller's call end operation (handset ON HOOK), the call end detection circuit 15a detects the call end due to the fact that the call current is no longer supplied, and the call end is detected. Based on the detected speech, the call current supply circuit 14a is turned off on the side of the key telephone 1, and the diode portion of the photocoupler PC1 is turned off to turn off the photocoupler PC1. When the photocoupler PC1 is turned off, the call current from the call current supply circuit 14a flows through the capacitor C1 to the transistor TR1 as a base current, and the transistor TR1 is turned on for a predetermined time until the charging of the capacitor C1 is completed. Then, the telephone equivalent impedance is applied between the extension lines 3-1 and 3-2. When the transistor TR1 is turned on, the impedance balance state is maintained for the predetermined time.

During this time, the call-end side starts the call-end processing based on the command generated when the call-end detection circuit 15a detects the call-end, but the call-end processing is required for the predetermined period. It is set to be sufficiently longer than the time, and the impedance balance state is maintained at least until the end of the call processing, so that the call loop is prevented from being opened. Therefore, while the call current supply circuit 14b on the called side continues to operate, the called party does not hear the howling sound generated from the speaker 10b with a built-in intercom and the service is improved.

[0017]

[Effect of device]

 As described above, according to the present invention, at the end of a mutual call between a plurality of telephones having an extension function, which are interconnected via an extension call path, the call loop is opened and the impedance balance may be lost. However, the call termination detection circuit detects the call termination, and based on the detection of the call termination, the impedance circuit on the telephone side that terminated the call is connected in parallel to the extension communication path for a predetermined time after the call termination. Therefore, the impedance balance of the call loop is maintained, howling is prevented, and service is improved until the end of call processing is completed on the phone that is still in the call state.

[Brief description of drawings]

FIG. 1 is a block diagram showing in principle the system configuration of a telephone device with a howling prevention function according to the present invention.

FIG. 2 is a circuit diagram illustrating a specific configuration of an end-of-call impedance circuit.

FIG. 3 is a timing chart for explaining the operation of the first embodiment.

FIG. 4 is a diagram for explaining a conventional technique.

[Explanation of symbols]

 1-button telephone (telephone with extension function) 2 door phone (telephone with extension function) 3-1 and 3-2 extension 4-1 and 4-2 extension 5 and 6 call circuit 7a and 7b hook switch 8a and 8b telephone circuit Network 9a, 9b Transmission / reception amplifier 10a, 10b Speaker 12a, 12b End-of-call impedance circuit 14a, 14b Speech current supply circuit 15a, 15b End-of-call detection circuit

Claims (1)

[Scope of utility model registration request] 1. In a telephone device in which a plurality of telephones having an extension function are interconnected via an extension communication path, an end-call detection circuit and an impedance circuit are provided in each of the telephones, and the impedance of the telephone side which has terminated the call first. A telephone device with a howling prevention function, characterized in that the circuit is connected in parallel to the extension communication path for a predetermined time after the end of the call.