JPS5856562A - Sound volume switch - Google Patents

Abstract

PURPOSE:To smooth the switching from the transmission to the reception state, by rectifying and smoothing a part of the transmission signal and subtracting the signal from an output of a reception smoothing circuit, in a sound volume switch circuit of a loudspeaker telephone set. CONSTITUTION:A sound volume switch circuit has a bypass preventing circuit 9 preventing bypass of a transmission signal to a reception circuit, and circuits 15, 16 rectifying and smoothing the transmission and reception signals, and compares the level of smoothed signals and inserts a loss to a channel. A part of the transmission signal is rectified and smoothed and subtracted from the output of a reception smoothing circuit 15, suppresses the increase in the reception circuit rectifying output due to bypass of the transmission signal, and the margin of a transmission blocking is increased, and the loss at the transmission state of a reception auxiliary variable loss 13 can be decreased, and the switching from the transmission to the reception state can smoothly be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a 7" switch circuit in a loudspeaker telephone.
1) A loudspeaker system using a microphone as a substitute for sending a call is known, and in such a loudspeaker telephone,
A voice switch 1g1Ayu is provided as means for preventing ringing. Figure 1 is a block diagram including a voice switch circuit of a conventional loudspeaker telephone, where l is a microphone, 2.
4.6.8.11 is increased! 3.12 is a transmitting and receiving #i-cho variable loss circuit, 5.13 is an auxiliary transmitting and receiving Ayu-cho variable loss circuit, 7 is a comparator, 9 is a protection side sound circuit such as a hybrid coil, 10 is the speaker, 14 is the town change medium equipment, mJ11c Sarel.

The transmission signal from the microphone 1 is amplified by the amplifier 2, inputted to the amplifier A 4 via the variable loss circuit 3, and the amplified output is sent to the line LINE via the side sound circuit 9.
It is transmitted to the other party's telephone via the exchange *1. Also, the #11f1 signal received from the other party's Toshiko machine via the line is variable amplified! 14 and is amplified by the amplifier 1 through the variable loss circuit 12.
1 and drives the speaker 10 with the amplified output.

In a single loudspeaker system, the sound from the speaker 10 is input to the microphone 1, and if the near end-to-circuit gain and the far-to-M circuit gain are different by 1 or more, no-ring occurs.

Note that the near-end loop gain is the gain of the loop in which the speaker 10 and the microphone l are coupled via the side-blocking sound circuit 9 of the own telephone, and the far-end loop gain is the gain of the loop in which the speaker 10 and the microphone 1 are coupled via the side-blocking sound circuit 9 of the own telephone. is the gain of the loop that includes the combination with .

In order to make the aforementioned near-end to loop gain and far-end to loop gain less than 1, a variable loss circuit 3 is provided in the transmitting circuit, a variable loss circuit 12 is provided in the receiving circuit, and a comparator 7 is used to compare the transmitting level and the transmitting level. When the transmitting level is compared with the receiving level, the loss of the variable loss circuit 3 is reduced and the variable loss circuit 12 is
When receiving a call, the loss of the variable loss circuit 3 is increased and the loss of the variable loss circuit 12 is controlled to be decreased due to the high reception level.

In addition, the sound during a call is not at a constant level continuously, but there are pauses during which there is no sound, and the variable amplifier 14 is operated at an automatic or manual level so that the output level of the speaker 10 can be controlled. If the gain of the variable p#1 width amplifier 14 is too large, a part of the transmitting signal will be transferred from the side sound circuit 9 to the variable amplifier MA 14. The received signal level may become larger than the input signal level input to the ratio IIR device 7θ, and the control states of the variable loss circuits 3 and 12 may be reversed. That is, transmission blocking may occur. On the other hand, when receiving a call, the speaker l.

If the voice from or a part of the surroundings is input to the microphone 1, and the transmitting level input is higher than the human receiving level of the comparator 7, receiving blocking may occur.

In order to prevent the above-mentioned sending/receiving pronking and receiving blocking, the loss of the -J variable loss circuit 5 is made small during sending, and the i
Just by reducing the loss of the loss circuit 13, the transmitting level input to the ratio IIR device 7 is made to be relatively larger than the receiving level input, and when receiving a voice, the above-mentioned relationship is reversed. lJ# is 0 in this case variable *=a
Even if the gain of 14 is maximized, the loss during transmission of the variable loss circuit 13 is selected so that blocking of the transmission does not occur. IiftIg7 circuits 1 and 16 include time constant circuits;
The output state of the comparator 7 is prevented from reversing during a short pause period during a call, and the hangover time is set to, for example, 200 to 300 membranes to prevent the end of the line from being cut off. Or when talking in a quiet state such as at night, it is common to reduce the gain of the variable amplifier 14. In that case, since the loss of the variable loss circuit 13 is normally controlled to be large during transmitting, even if a receive signal arrives, the receive level input to the comparator 8 will be reduced due to the large loss of the variable loss circuit 13. In some cases, the level does not become higher than the transmitting level input, and even if the variable amplifier 14t is used, it may not be possible to switch to the receiving state.

The present invention provides a voice switching circuit for the above-mentioned loudspeaker telephone, regardless of the gain of the amplifier in the receiving circuit.
The purpose of this is to smoothly switch from a listening state to a listening state.

In order to achieve the above object, the present invention includes a side sound prevention circuit that prevents the transmitting signal from entering the receiving circuit, and a circuit that rectifies and smoothes the transmitting signal and the receiving signal. In a voice switch circuit that compares the levels of half-absorbed/C signals and inserts a loss into the communication circuit, a part of the transmitting signal 1G is in-stream flat and is generated from the A'+I receiving smooth circuit output. Particularly, the present invention is characterized by suppressing an increase in the output of the receiver circuit due to the inclusion of 1M9 in the transmitting signal.

The present invention will be explained in detail below using examples.

FIG. 2 is a block I@1 diagram of the audio switch circuit according to the embodiment of the present invention. In the figure, the same reference numerals as in FIG. 1 indicate the same parts, 17 is a distorted current circuit consisting of resistors r, R, capacitor C1, etc., 21 is a differential amplifier, 22 is a variable amplifier, The gain of this variable amplifier 22 is 6f and the width is 414.
It is linked to the profit of Send ifl with output of comparison a7! i
The bad thing is that when controlling the receiving variable loss circuit 3.12 and the auxiliary variable loss circuits 5, 13, the output of the transmitting variable loss circuit 3 and the receiving signal from the side sound protection circuit 9 (which suppresses spider noise) In this way, according to the circuit according to the invention, the transmitting block is As the P cooking margin increases, the reception auxiliary variable loss 13
The loss in the 0-transmission state can be reduced, and the sensitivity to interference by the reception signal in the transmission state is increased, which has a great effect.

[Brief explanation of the drawing]

Figure ag1 is a block diagram of a conventional audio switch circuit;
The figure is a block diagram of an audio switch circuit that is an embodiment of the present invention. l;Microphone, 2.4* 6* 8@lZ
: Multiplier, 3.12; Transmission and reception of variable loss circuit,
6゜13; Auxiliary transmission and auxiliary costs - variable loss 1gl road, 7
; Comparator, 9; Circuit for prevention 11411, 15, 16.17
; Rectifier circuit, 14, 22; Variable amplifier, 21; Differential amplifier aO

Claims (1)

[Claims] A side sound prevention circuit that prevents the transmitting signal from entering the receiving circuit, and the transmitting and receiving signals! In the voice switch circuit which includes a smoothing circuit and which compares the level of the smoothed signal and inserts a loss into the speech circuit,
A voice switch circuit which suppresses an increase in the output of the receiving signal 11al due to the one-way input of the sending signal by rectifying and smoothing a part of the signal and subtracting it from the output of the receiving smoothing circuit. .