JPS59125146A - Transmission and reception switching device - Google Patents

Abstract

PURPOSE:To detect a click sound generated during the transmission/reception switching with addition of a simple circuit constitution, by controlling the level of the line input signal with use of the output of a transmission/reception control circuit. CONSTITUTION:The sound signal supplied from a mike 14 is delivered to a line via a switch SW1. While the speech receiving signal is supplied from a line, and this receiving signal is compared with the speech transmitting signal by a transmission/reception control circuit 7. When the speech receiving signal has a high level, the control output is set at L level. As a result, the SW1 and SW2 of a switching circuit 6 are turned off and on respectively. Then the speech transmitting signal is cut, and the speech receiving signal is delivered to a speaker 15 via an amplifier 5. In this case, a TR13 is slowly turned off by the charged electric charge of a capacitor 12. This can prevent the click sounds which are generated when the switching is carried out between transmission and reception.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a transmitting/receiving switching device for a telephone device, an intercom device, etc., which uses a built-in microphone and speaker to switch between sending and receiving calls, regardless of the handset and receiver. It is related to.

2. Description of the Related Art Configuration and Problems Therein In a conventional device of this type, a circuit for preventing click noise caused by a changeover switch due to DC fluctuations, etc. is known.

However, in this method of switching between transmitting and receiving by detecting the level of the audio signal, when a large signal suddenly comes in, a clicking sound is generated at the rising edge of the switching, which is unpleasant to the ears.

OBJECT OF THE INVENTION The object of the present invention is to eliminate the above-mentioned conventional click sound that occurs when switching between transmitting and receiving audio signals by adding a simple circuit configuration without affecting the transmission and reception of signals. be.

Structure of the Invention In order to achieve the above object, the present invention controls the line input signal level by the output of a transmission/reception control circuit that determines transmission/reception switching.

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

Figure 1 shows the transmission/reception switching circuit device inside the telephone;
The figure shows the output waveform at the time of switching. In Fig. 1, 1 is a hybrid transformer circuit inside the telephone;
, 3 are amplifiers for transmitting calls, 4 and 6 are amplifiers for receiving calls, and 6 is two switches SW for switching between transmitting and receiving calls.
1. A changeover switch circuit with SW2; 7 a transmitting/receiving control circuit that compares the transmitting and receiving signal levels and determining whether to switch between transmitting and receiving; 8, 9, 10.11 each resistors; 12
13 is a capacitor, 13 is a transistor, 14 is a transmitting microphone, and 15 is a receiving speaker.

Now, if we consider the case of switching from the transmitting state to the receiving state,
In the transmitting state, the switch SW1 of the changeover switch circuit 6
is ON and switch SW2 is OFF, the audio signal input from microphone 14 is sent to amplifier 3. Switch SW1.
The signal passes through the amplifier 2 and is output from the hybrid transformer circuit 1 to the line.

On the other hand, since the switch SW2 is OFF, no received signal is applied to the speaker 15.

Here, when a reception signal comes in from the line, it passes through the vibe υ sodo transformer circuit 1 and is input to the INA of the transmission/reception ff1lJ control circuit 7. Also, the transmitting signal is input to INN B from the output of amplifier 3, and the transmitting signal,
By comparing the received signal and the received signal, if the received signal is large, the control output o
ut becomes Low level. (Hf (7h) in the transmitting state
level), so that the switching circuits switch SW1
Ka OFF , , Z, If SW2 Ka ON To f
z Re, the transmitting signal is cut and the receiving signal is switched to switch S.
It passes through W2, is amplified by amplifier 6, and outputs to speaker 16.

FIG. 2 shows signals in this series of circuit operations. A shows the cuff for the control circuit, and B shows the speaker output waveform without the click noise prevention circuit.

Here, if the received signal is large, the level of the B waveform becomes large, so the rising portion is output to the speaker as a click sound.

Now, in the transmitting state, the transmitting/receiving control circuit 7 in FIG.
At this time, the transistor 13 is in the ON state due to the resistance 8°9.10. In this case capacitor 1
2 is charged.

When switching from this state to receiving, the control output of the transmitting/receiving control circuit 7 becomes Low level, but the transistor 13 is slowly turned off by the discharge current of the capacitor 12. Therefore, the reception signal becomes the signal shown in C in Fig. 2,
Click sounds are prevented.

Effects of the Invention The present invention has the above-mentioned configuration, and it is possible to prevent a click sound from occurring at the rising edge of the switching when a large signal suddenly enters when switching between transmitting and receiving by simply adding a circuit. It is something that can be done.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a transmission/reception switching device according to an embodiment of the present invention, and FIG. 2 is a waveform diagram of its essential parts. 1...Hybrid transformer circuit, 6...
Changeover switch circuit, 7...Transmission/reception control circuit, 12
...Capacitor, 13...-Transistor.

Claims (1)

[Claims] A transmitting/receiving selector switch, a transmitting/receiving control circuit for determining whether to switch between transmitting/receiving and controlling the transmitting/receiving selector switch, and means for controlling a line input signal level using an output signal from the transmitting/receiving control circuit. Transmission/reception switching device.