JPH06225353A - Key telephone system - Google Patents

Abstract

PURPOSE:To prevent a howling phenomenon in a key telephone system by reducing a sound feedback quantity to sneak in from a sound output circuit to a microphone circuit on the whole. CONSTITUTION:In the key telephone system 36, a feedback quantity adjustment circuit 38 is installed between the sound output circuit 33 and a microphone device 34. The signal of the same level and an opposite phase as/to the acoustic feedback quantity to sneak from the sound output circuit 33 to the microphone device 34 and the signal having passed through the microphone circuit 34 are superposed forcedly on each other in the feedback quantity adjustment circuit 38. By the operation, the acoustic feedback quantity sneaking from the sound output circuit 33 to the microphone device 34 is made small.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a public telephone line, PBX.
The present invention relates to a key telephone device including a main device that accommodates a station line from a line or the like and a plurality of key telephones connected to the main device.

[0002]

2. Description of the Related Art FIG. 3 shows the configuration of a conventional key telephone device. In FIG. 3, since the key telephone device 1 and the key telephone device 2 have the same configuration, the configuration description of the button telephone device 2 will be omitted in the configuration description of the button telephone device 1.

The main unit 3 is composed of a link set 4, a communication circuit 5 and a station line interface circuit 6.

The handset 7 comprises a receiver 8 and a transmitter 9. The monitor 10 includes a speaker circuit 11 and a microphone circuit 12. The speaker circuit 11 converts the sent electric signal into an acoustic signal.
The microphone circuit 12 converts an acoustic signal into an electric signal.

The handset voice amplifier 13, the handset voice amplifier 14, the monitor voice amplifier 15, and the monitor voice amplifier 16 amplify the levels of the electric signals respectively sent.

The monitor volume 17 adjusts the level of the electric signal sent to the speaker circuit 11. The speech path switching circuit 18 and the speech path switching circuit 19 switch the speech path to the handset side or the monitor side.

The 2-wire / 4-wire conversion circuit 20 separates and synthesizes an electric signal sent from the main unit 3 or sent to the main unit 3 into the receiving side or the transmitting side.

Next, the operation of the above conventional example will be described.
In FIG. 4, a key telephone device 1 to a key telephone device 2
A talkback operation for responding to a voice call to the will be described.

The acoustic signal input to the transmitter 9 is converted into an electric signal, and the level of the signal is amplified by the handset transmitter amplifier 14. The amplified electric signal is sent to the main device 3 via the communication path switching circuit 19, the two-line / four-round conversion circuit 20.

The electric signal is sent from the main unit 3 to the key telephone unit 2.
2 line / 4 conversion circuit 21, speech path switching circuit 22,
It passes through the monitor volume 24. This monitor volume 2
The electric signal passing through 4 is passed through the monitor reception amplifier 27, converted into an acoustic signal by the speaker circuit 33 in the monitor 32, and output.

In the case of talkback transmission, the acoustic signal is converted into an electric signal by the microphone circuit 34 and amplified by the monitor transmission amplifier 28. The electric signal passes through the communication path switching circuit 23, the two-line / four-line conversion circuit 21, and the main unit 3
Sent to.

A case of a normal extension call from the key telephone device 1 to the key telephone device 2 will be described.

The electric signal sent from the key telephone device 1 via the main unit 3 is sent to the speech path switching circuit 22 via the 2-line / 4-line converting circuit 21. The sent electric signal is converted into an acoustic signal from the handset 30 in the handset 29 through the handset receiver amplifier 25 and sent out.

Next, a case of a normal extension call response from the key telephone device 2 to the key telephone device 1 will be described.

An acoustic signal is transmitted to the transmitter 31 in response to the acoustic signal transmitted from the receiver 30. The acoustic signal is amplified by the handset transmission amplifier 26, passes through the speech path switching circuit 23, the two-line / four-line conversion circuit 21, and then the main unit 3
Sent to.

An electric signal sent from the main unit 3 to the key telephone unit 1 passes through a 2-line / 4-round conversion circuit 20 and a speech path switching circuit 18. Next, the electric signal is amplified by the handset receiver amplifier 13 and converted into an acoustic signal by the receiver 8.

As described above, the speaker circuit 33 outputs the acoustic signal. In that case, a part of the acoustic signal is
Each goes around to the microphone circuit 34. A loop is formed in the speech path in the key telephone device 21 due to the wraparound of the acoustic signal, and howling occurs when the overall loop gain of the loop exceeds 1.

Therefore, in the conventional key telephone device, the loop gain is set to 1 or less and the howling is prevented by keeping the distance between the speaker circuit 33 and the microphone circuit 34.

[0019]

However, in the above-mentioned conventional button telephone device, the speaker circuit 33 has a large output so that a voice call can be heard even in a noisy office, and the microphone circuit 34 also responds to the voice call. Since the sensitivity is high enough to be heard even in a noisy office, there is a problem that the howling phenomenon easily occurs when the size is reduced.

The present invention solves such a conventional problem, and the distance between the speaker circuit 33 and the microphone circuit 34 is short due to miniaturization, and the microphone circuit 34 is small.
It is an object of the present invention to provide an excellent button telephone device capable of preventing the howling phenomenon even when the audio signal sent from the speaker circuit 33 is easily captured.

[0021]

In order to achieve the above object, the present invention provides a speaker circuit between a speaker circuit for converting an electric signal into an acoustic signal and a microphone circuit for converting an acoustic signal into an electric signal. A feedback amount adjusting circuit is provided which changes the level or phase of the electric signal converted into the acoustic signal and superimposes the changed electric signal on the electric signal converted by the microphone circuit.

[0022]

By the above means, the feedback amount adjusting circuit is provided between the speaker circuit and the microphone circuit, and the speaker circuit forcibly outputs the signal of the same level and the opposite phase to the output signal of the speaker circuit which goes around to the microphone circuit. From the speaker circuit to the microphone circuit, the amount of sneaking of the acoustic signal from the speaker circuit to the microphone circuit is reduced as a whole.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, description of the same numbers and names as those in FIG. 3 is omitted. The button telephone device 35 and the button telephone device 36 have the same configuration.

The feedback amount adjusting circuit 37 includes a voice output circuit 11
And the microphone circuit 12, the feedback amount adjusting circuit 38 includes a voice output circuit 33 and a microphone circuit 34.
It is provided between.

Next, the operation of the above embodiment will be described.
In FIG. 1, a talkback operation for responding to a voice call from the key telephone device 35 to the key telephone device 36 will be described.

The electric signal converted from the acoustic signal by the transmitter 8 is amplified by the handset transmitter amplifier 13 and is sent to the main unit 3 via the speech path switching circuit 18 and the 2-wire / 4-wire converting circuit 20. .

The electric signal passed through the main unit 3 is sent to the key telephone unit 36, and passes through the 2-line / 4-line conversion circuit 21, the speech path switching circuit 22, and the monitor volume 24. The electric signal passed through the monitor volume 24 is amplified by the monitor reception amplifier 27, converted into an acoustic signal by the audio output circuit 33, and output.

Also, in the case of talkback transmission, the electric signal performs the above operation. As described above, according to the above-described embodiment, a part of the acoustic signals output from the speaker circuit 11 and the speaker circuit 33 is generated by the microphone circuit 1 respectively.
2. Go around the microphone circuit 34. The circulated acoustic signal is the microphone circuit 12 and the microphone circuit 3
At 4, it is converted into an electric signal. By forcibly sending electric signals of the same level and opposite phase with respect to the level and phase of the electric signal to the microphone circuit 12 and the microphone circuit 34, as a whole, the speaker circuit 11 and the speaker circuit 33 to the microphone circuit 12. There is an advantage that the amount of feedback to the microphone circuit 34 can be reduced.

[0029]

As is apparent from the above embodiment, the present invention provides the feedback amount adjusting circuit between the speaker circuit and the feedback amount adjusting circuit, which has the same level and opposite phase to the output signal of the speaker circuit which goes around to the microphone circuit. Forcibly sending the signal from the speaker circuit to the microphone circuit reduces the amount of feedback from the speaker circuit to the microphone circuit as a whole. Even when the amount of signal returned to the microphone circuit is large, howling can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of a key telephone device according to an embodiment of the present invention.

FIG. 2 is a schematic circuit diagram in the operation of the button telephone device.

FIG. 3 is a schematic circuit diagram of a conventional key telephone device.

FIG. 4 is a schematic circuit diagram in the operation of the button telephone device.

[Explanation of symbols]

 3 Main device 7,29 Handset 8,30 Handset 9,31 Transmitter 10,32 Monitor 11,33 Voice output circuit 12,34 Microphone circuit 35,36 Button telephone device 37,38 Feedback amount adjusting circuit

Claims (1)

[Claims] 1. A speaker which receives an electric signal transmitted from the other key telephone device via a main device, converts the electric signal into an audio signal for voice call or a call, and outputs the acoustic signal. A circuit, a microphone circuit for converting an acoustic signal of the response of the voice call or the call into an electric signal and sending it to the key telephone device via the main unit, and an acoustic signal of the voice call or the call Of the above-mentioned signal, and a feedback amount adjusting circuit for superimposing a signal having the same level and an opposite phase to the above-mentioned signal on the overlapping signal.