JPS6066560A - Sound coupling preventing circuit - Google Patents

Abstract

PURPOSE:To make the structure of a box simple and to reduce influences of sound coupling in two-way speech system by preventing sound coupling of a speaker and a microphone of receiving side electrically. CONSTITUTION:A comparator circuit 12 compares output signals of detecting circuits 9, 10, and if judged to be transmitting state, output of a switching circuit 11 turns a switch 3 on and turns a switch 6 off. Thus, an output signal of a microphone amplifier 2 is transmitted to a speaking device B of opposite side. At this time, voice caused by sound coupling of the device B is inputted to the detecting circuit 10. However, output of the detecting circuit 9 is inputted to a controlling circuit 13 simultaneously with becoming on of the switch 3, and the circuit 13 outputs a controlling signal that stops action of the detecting circuit 10. Accordingly, above-mentioned voice input signal does not turn a switch 6 of receiving side on. When signals from a microphone 1 give out and output of the detecting circuit 9 becomes lower than threshold value of the comparator circuit in the controlling circuit 13, and above-mentioned controlling signal from the controlling circuit 13 becomes nil, the detecting circuit 10 outputs a detection signal to the comparator circuit 12.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an audio coupling prevention circuit for a two-way communication device that switches the direction of communication using an audio switch.

Conventional flJ configuration and its problems Conventional two-way communication devices using audio switches require the microphone and speaker to be installed in the same small housing, so the acoustic coupling between the microphone and speaker causes the output from the speaker to be reduced. is fed back to the microphone, and there are many malfunctions such as the sound acting as if it were being input, or cutting off the beginning or end of a sentence.

The path of such acoustic coupling is shown in FIG. Route a is the interview return of the 13 voices output by speaker S,
The path b is a return via the inside of the casing B, the path C is a return reflected from an object such as an external wall, and the path d is a return via the casing B. In actual equipment, the housing B in which the microphone M and speaker S are installed is often a small sealed container, so the feedback HH via the inside of the housing B is the largest and is the biggest factor that causes the above malfunction. 4
In order to attenuate this acoustic coupling, acoustically blocking structures between the microphone and the speaker have been devised, but they are incomplete and expensive, causing problems.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned drawbacks and improves the housing structure to 177'i.
111, it is an object of the present invention to provide an inexpensive acoustic coupling prevention device for a two-way communication device that is less affected by acoustic coupling.

Structure of the Invention In the present invention, in a two-way communication device that switches between a transmitting state and a receiving state using an audio switch, a microphone input on the transmitting side is detected and the audio output signal is transmitted from the speaker on the receiving side to the microphone on the receiving side. The present invention is characterized in that the operation of the microphone input detection circuit on the receiving side is stopped using the microphone input detection signal on the transmitting side while acoustic feedback is being fed back due to coupling, thereby preventing acoustic feedback.

DESCRIPTION OF EMBODIMENTS An acoustic coupling prevention circuit according to an embodiment of the present invention will be described below with reference to the drawings.

A first embodiment is shown in FIG. In the figure, 1 is a microphone, 2 is a microphone amplifier, 3 is a transmitter switch, 4 is a transmitter amplifier,
6 is a receiving preamplifier, 6 is a receiving side switch, 7 is a receiving amplifier, and 8 is a speaker.

1, 9 and 10 are audio signal detection circuits, 11 is a switch circuit, and 13 is a control circuit. 14 is a speaker of another communication device, and 15 is a microphone.

Next, the operation of this circuit will be fully explained.74 A human input voice signal inputted from the microphone 1 to the communication device is amplified by the microphone preamplifier 2, and inputted to the detection circuit 9 where it is detected. The output signal is compared with the output signal of the detection circuit 10 in a comparison circuit 12, and if it is determined that the transmitting state is established, the switch circuit 11
A signal for turning on the transmitting side switch 3 and turning off the receiving side switch 6 is output from the terminal. From this k, the output signal from the microphone amplifier 2 passes through the transmitter side switch 3 ( ), is amplified by the transmitter amplifier 4, and is sent out from the transmitter end, resulting in phase q = ++
+1+Telephone deviceTelephone device-transmitted to the car 14 and output.

At this time, the speaker 14 is connected to the microphone 15 by acoustic coupling.
The audio output from the receiver preamplifier 5 is amplified and input to the detection circuit 10, but at the same time as the transmitting switch 3 is turned on, the output of the detection circuit 9 is input to the control circuit 13.
As a result, the control circuit 13 outputs the signal to the detection circuit 1.
Since a control signal is output that does not cause output of the detection signal to o, the acoustically coupled audio signal is no longer input to the comparator circuit 12, and the acoustically coupled audio input signal does not turn on the receiver switch 6. The audio input signal from the microphone 1 disappears, the detection signal level of the detection circuit 9 falls below the threshold of the comparison circuit in the control circuit 13, and the control circuit 1
When the control signal that does not cause the detection circuit 10 to output all detected signals from the detection circuit 3 disappears, the detection circuit 10 outputs all detected signals to the comparison circuit 12VC. - Similarly, the audio signal input from the microphone 15 of the communication device B is output from the receiving end to the receiving preamplifier 6, the receiving side switch 6, the receiving amplifier 7, and the speaker 8, and is further outputted from the microphone 15 by acoustic coupling. 1 is input as an audio signal, but since a control signal that does not output all the detection coefficients to the detection circuit 9 is output from the control n path 13, the output of the detection circuit 9 (+9 is not input to the comparison circuit 12). , the transmitting side switch 3 will not be turned on.

Is FIG. 3 a block diagram of a specific circuit of the control circuit 13 in FIG. 2? show. Reference numerals 16 and 18 are comparison circuits, 17° and 19 are delay circuits, and 20 is a control signal generation circuit.

Note that the same parts as in the embodiment shown in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted. Figure 4 is similar to Figure 3 (a~
] is a waveform diagram of each point.

Next, the operation of this control circuit 13 will be explained.

The detection signal (a) output from the detection circuit 9 is sent to the comparison circuit 1.
6, and when all the thresholds are exceeded, the comparator circuit 16 outputs (i (e)
) is output and delayed by the delay circuit 17. j
(cr) and is input to the control circuit 2o. At this time, if the transmitter switch 3 is on, the control circuit 20 outputs a signal (i) that does not output the detection signal (C) of the detection circuit 10, and the output signal (a) of the detection circuit 9 is sent to the comparison circuit. 16 and the output signal of the delay circuit 17 (
It is output when q) disappears. Next, the detection signal (C) output from the detection circuit 10 enters the comparison circuit 18V, and when it exceeds the threshold, the signal (f) is output from the comparison circuit 18, and the signal (h) delayed by the delay circuit 19 becomes the control circuit. 2o
is input. At this time, if the receiver switch 6 is on, the detection signal (a) from the detection circuit 9 is sent from the control circuit 20.
The signal (i) that does not cause k to be output is output, the output signal (c) of the detection circuit 16 becomes lower than the threshold of the comparison circuit 18, and the output signal (h) of the delay circuit 19 disappears.

As a result, the above switching is performed.

Next, a second embodiment of the present invention is shown in FIG.

21, 22, 23, and 24 are detection circuits, and 26 is a sequential circuit. Note that the same parts as in the first embodiment are denoted by the same reference numerals and the explanation thereof will be omitted. Figure 6 is shown in Figure 5.
It is a waveform diagram of each point of P.

Next, the operation of this circuit will be explained. The configuration of the audio switch circuit shown in FIG. 5 uses all of the sequential circuits 25,
In this case, the acoustic coupling prevention circuit 13 needs detection, comparison, and control functions. The audio signal input to the microphone 1 of the communication device C is amplified by the microphone amplifier 2, becomes a signal (k), is input to the acoustic coupling prevention circuit 13, is detected, and is compared with a threshold value (If it reaches a high signal from the switch circuit 11). (The force is output, the transmitter switch 3 is turned on, and a High signal (0) is output from the acoustic coupling prevention circuit 13, causing the detection circuit 23
Stop the output.

Furthermore, the audio output from the speaker 14 of the communication device is input to the microphone 15 by acoustic coupling, and becomes a signal amplified by the reception amplifier 5), and is input to the acoustic coupling prevention circuit 13, where it is detected and compared. Acoustic coupling prevention circuit 13
A high signal (0) is output from the detection circuit 23, and the output of the detection circuit 23 is stopped. The signal (0) that stops the output of the detection circuit 23 is output from the acoustic coupling prevention circuit 13 from Logic 1 of the signals whose envelopes were detected within the coupling prevention circuit 13.Similarly, the voice signal from the microphone 15 of the communication device enters the communication device C and is detected by the detection circuit when the receiver 4111 switch 6 is turned on. 21 is stopped, and the detection circuit 21 does not output a signal at 1 when the signal due to acoustic coupling of the microphone amplifier 2 becomes lower than the threshold of the acoustic coupling prevention circuit 13. Therefore, the detection circuit 21 does not output a signal. Danger (1 commotion,
1- Prevent malfunctions caused by overlapping.

Effects of the Invention As mentioned above, the present invention provides a simple method for removing the microphone and speaker and a simple structure of the housing in order to electrically prevent acoustic coupling between the speaker and the microphone on the receiving side. , assembly man-hours can be reduced and economicalization can be promoted.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the path of acoustic coupling in a two-way communication device, Fig. 2 is a block diagram of the acoustic coupling prevention circuit according to the first embodiment of the present invention, and Fig. 3 is a detailed diagram of the main parts thereof. A block diagram of the circuit, Figure 4 is a waveform diagram of each point shown in Figure 3,
Figure 6 is the second fruit/11! The block diagram of example i, FIG. 6, is a waveform diagram of each point shown in FIG. 1.16・Microphone, 2・・Microphone amplifier, 3・−・
Sending side switch, 4...Sending amplifier, 5...Receiving preamplifier, 6. Receiving side switch, 7...
Receiving 1. Zan amplifier, 8, 14... speaker, 9, 10
゜21.22.23.24...Detection circuit, 11...
...Switch circuit, 12.16.18... Comparison circuit, 13. Yd leg coupling prevention circuit, 17.19. White delay circuit, 20. Control circuit, 2!5 Order 11. Circuit 5 , Name of agent: Patent attorney Toshio Nakao and one other person Section 1 Section 2 Figure 3 J

Claims (1)

[Claims] The transmitting state is switched by an audio switch circuit that detects all microphone inputs and automatically switches, and also detects all microphone inputs on the transmitting side and sends the audio output signal from the speaker on the receiving side to the microphone on the receiving side. 1. An acoustic coupling prevention circuit characterized in that the operation of a microphone input detection circuit on a receiving side is stopped using a microphone input detection signal on a transmitting side to prevent acoustic feedback while feedback is being caused by coupling.