JPH037310B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a voice switch circuit used in two-way communication devices such as intercoms and loudspeaker telephones.

Configuration of Conventional Example and Its Problems An example of a voice switch circuit in a conventional two-way communication device is shown in FIG. In the figure, 1 is a microphone, 2 is a microphone amplifier, 3 is a transmitting side variable insertion loss or switch, 4 is a transmitting amplifier, 5 is a receiving preamplifier, 6 is a receiving side variable insertion loss or switch, 7 is a receiving amplifier, 8 1 is a speaker, 9 is a transmitting detection circuit, 10 is a comparison circuit, 11 is a receiving detection circuit, and 12 is a switch circuit.

In this circuit, a comparison circuit 10 compares the signal levels of a signal detected by a detection circuit 9 from the microphone amplifier output and a signal detected by a reception detection circuit 11 from the reception preamplifier output, and a switch is activated according to the comparison output. The circuit 12 is switched to control the variable insertion loss or switch 3 on the transmitting side and the variable insertion loss or switch 6 on the receiving side. For this reason, this circuit has problems in that it often malfunctions due to ambient noise and acoustic coupling between the microphone and the speaker, has many adjustment points during assembly, and is difficult to adjust.

OBJECT OF THE INVENTION The present invention eliminates the conventional drawbacks as mentioned above,
To provide a voice switch circuit suitable for a two-way communication device that is easy to assemble and adjust.

Structure of the Invention In the present invention, a signal that detects a microphone amplifier output signal, a signal that detects a receiver amplifier output signal, a signal that detects a transmitter amplifier output signal, and a signal that detects a receiver preamplifier output signal is used. The device is characterized in that the transmission direction is determined by detecting the order of occurrence, and as a result, there are fewer malfunctions due to surrounding noise, and there are fewer adjustment points, making assembly easier.

DESCRIPTION OF THE EMBODIMENTS An audio switch circuit according to an embodiment of the present invention will be described below with reference to the drawings. In Fig. 2, 13, 14, 15, 16 are detection comparison circuits;
7 is a sequence detection circuit. Note that the same parts as in the conventional example are designated by the same reference numerals as in FIG. 1, and the explanation thereof will be omitted.

Next, the operation of this circuit will be explained. The audio input signal input to the microphone 1 is amplified by the microphone amplifier 2 and applied to the detection comparison circuit 13. Here, if the signal level is higher than the setting, a high level detection signal is output to point a. At this time, the detection comparison circuit 14
If the output b of the output b and the output c of the detection comparison circuit 15 are at a low level, the order detection circuit 17 determines that the transmitting state is in progress, and the switch circuit 12 reduces the variable insertion loss on the transmitting side or the insertion loss of the switch 3. or turn it on, increase or turn off the receiving side variable insertion loss or the insertion loss of switch 6, and set the device to the transmitting state.

Similarly, when there is an input from the microphone at the receiving end, the output of the receiving preamplifier 5 is output to the detection comparison circuit 1.
5, and if the signal level is above the set value, a high level signal is output to point c. At this time,
If the output d of the detection comparison circuit 16 and the output a of the detection comparison circuit 13 are at a low level, the sequential circuit 17 determines that the call is in the receiving state, and the switch circuit 12 determines the transmission side variable insertion loss or the insertion loss of the switch 3. The receiver variable insertion loss or the insertion loss of switch 6 is increased or turned off, and the device is set to the listening state.

FIG. 3 shows the order detection circuit 17 and a switch circuit diagram. In FIG. 3, 18 and 19 are delay circuits;
20, 21 are 3-input NOR gates, 22, 23 are
AND gates 24 and 25 are NOR gates.
FIG. 4 is a waveform diagram of each point a to f shown in FIG. The condition for the voice switch to change to the transmitting state is only in the case of a・′・′・, and the condition for the voice switch to change to the receiving state is c・′・
Only in the case of d.

Effects of the Invention As described above, according to the present invention, depending on the combination of the presence or absence of the microphone amplifier output signal, the transmitting amplifier output signal, the receiving preamplifier output signal, and the receiving amplifier output signal, the receiving state or the transmitting state can be determined. Since the signal loss in the receiving and transmitting channels is controlled by determining whether or not the transmission is occurring, it is possible to switch between transmitting and receiving with fewer malfunctions.

In other words, in a system that judges the receiving and transmitting states based on the magnitude of the level between the outputs of each amplifier, the comparison is a relative comparison between the outputs of both amplifiers. During reception, if a large input occurs due to an elbow or the like accidentally hitting the receiving microphone, the receiving state will be switched to the transmitting state.

In this regard, according to the present invention, in the receiving state, when normal audio is being received, even if a large input is applied to the receiving microphone as described above, the transmitting state cannot be switched.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional audio switch circuit, FIG. 2 is a block diagram of an audio switch circuit according to an embodiment of the present invention, FIG. 3 is a specific circuit diagram of the order detection circuit and switch circuit, and FIG. FIG. 4 is a waveform diagram of signals at each point in FIG. 1...Microphone, 2...Mic preamp, 3...
...Sending side variable insertion loss or switch, 4...
Transmitting amplifier, 5... Receiving preamplifier, 6... Receiving side variable insertion loss or switch, 7... Receiving amplifier, 8... Speaker, 9, 11... Detection circuit, 10... Comparison circuit, 12... Switch circuit,
13, 14, 15, 16...comparative detection circuit, 17
... Sequential circuit, 18, 19 ... Delay circuit, 20,
21...NOR gate, 22,23...AND gate, 24,25...NOR gate.

Claims (1)

[Claims] 1. When the microphone amplifier output signal, the transmitting amplifier output signal, the receiving preamplifier output signal, and the receiving amplifier output signal of the two-way communication device are each at a predetermined level or higher, the first, second, and
a detection comparison circuit that generates third and fourth detection signals; and a detection comparison circuit that reduces loss in a transmission path under the condition that the first detection signal exists and the second and third detection signals do not exist. increases the loss in the receiving line,
a switching means for reducing the loss in the receiving path and increasing the loss in the transmitting path under the condition that the third detection signal is present and the first and fourth signals are not present. switch circuit.