JPS6066562A - Voice switch circuit - Google Patents

Abstract

PURPOSE:To eliminate malfunction due to sound coupling and noise by turning a transistor on and off using a controlling signal that controls direction of talking and giving hysteresis characteristic by changing reference voltage of a comparator. CONSTITUTION:Signals a, b from the master machine of an interphone to a slave machine and signals c, d of reverse direction are set respectively to smoothing circuits 11, 13, 15, 17 and the output is inputted to comparator circuits 12, 14, 16, 18. As mentioned later, the comparator circuits output signals of ''H'' and ''L'' depending on the presence or absence of an aural signal. Direction of talking is determined by a controlling circuit 19 using this signal, and the direction of talking is changed by inputting the ''H'' signal and ''L'' signal reciprocally to analog switches 3, 8. In comparator circuits 12, 16 the output of the smoothing circuit 11 is inputted to a plus (+) terminal of a comparator 34. When this input becomes higher than the reference voltage, an ''H'' signal is outputted, and ''H'' signal is outputted from the terminal 24 of the controlling circuit 19, and ''L'' signals is outputted simultaneously from the terminal 25. At this time, a Tr31 of the circuit 12 is turned on by the ''H'' signal of the terminal 24 and reference voltage is lowered. At the same time, the ''L'' signal of the terminal 25 turns the Tr31 of the circuit 16 off and heighten the reference voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a conventional configuration of an audio switch circuit that completely controls switching between the transmitting direction and the receiving direction depending on the audio signal level of the transmitting path and the receiving path. Conventionally, as shown in FIG. 1, for example, the transmitting signal passes through the rectifying and smoothing circuit 11 and is input to the terminal 20 of the comparator circuit 12, and the receiving signal also passes through the rectifying and smoothing circuit 17 for comparison. circuit 1
2 terminal 21 was manually connected. According to this, since the 1° terminal 210 level rises above the terminal 20 level during the receiving state, the comparator circuit 12 inserts a certain loss into the variable loss circuit 3', and the loss of the variable loss circuit 9' is zero. When in the transmitting state, the terminal 200 level is higher than the terminal 210 level, so JAIS,
+1 times j'i'i12 are all zeros of the variable loss circuit 3' (1), and a constant loss is inserted into the variable loss circuit 9'.

The operation of the comparator circuit is shown in FIG. 2, where the horizontal axis represents time and the vertical axis represents the rectified, smoothed, signal level. At first, the signal level at terminal 2Q is high and it is in the transmitting state, but at point a, where the conversation does not end, the signal level at terminal 21 becomes even higher and the state switches to the receiving state. 2. External conditions such as ambient noise change. ), there have been problems such as malfunctions such as entering the receiving state while transmitting a call, resulting in speech breakage and the conversation not being able to proceed smoothly. An object of the present invention is to realize an audio switch circuit that can eliminate the noise and switch without causing malfunction even in response to changes in external conditions. , the fully rectified and smoothed signal is connected to one input terminal of the comparator, connected from the DC power supply terminal to the other input terminal of the comparator via a resistor, and from this input terminal two 1-1 columns are connected. All resistors connected to the valve are grounded,
By connecting the collector of a transistor to the connection point of the two series-connected resistors, grounding all of its emitters, and inputting a control signal for controlling all communication directions to its base through the resistor, the transistor is turned on and off. This provides flexibility so that once the direction of communication is determined, the direction of communication does not change during the conversation.

DESCRIPTION OF EMBODIMENTS Hereinafter, one embodiment 17/11 of the present invention will be explained with reference to the drawings. In FIG. , a part of the signal sent to the speaker 5 of the intercom slave unit, a part of the signal after passing through the amplification 2;;7 of the signal from the micro of the intercom slave unit, and a part of the signal sent to the speaker 1o of the intercom base unit. rectifying and smoothing circuits 11, 13,
15. Input to 17 and its output all ratio 1 bit circuit 1
Enter 2,14°16.18. Each comparison circuit 12°i4, 16.18 outputs a high level signal or a low level signal depending on the presence or absence of an audio signal. The control circuit 1 uses these four high level or low level signals.
9 determines the call direction, and by inputting all high-level and low-level signals reciprocally to the control terminals 2' and 6.27 of the analog switches 3 and 8, the analog switches 3 and 8 are turned on and off reciprocally. and change all intercom communication directions.

FIG. 4 is a circuit diagram of the ratio 1 bit circuit 12.16, and FIG. 5 is its operating waveform diagram. So, first, when a signal is input from microphone 1, it is rectified by amplifier 2.

The audio signal (FIG. 6) that has passed through the smoothing circuit 11 is input to the terminal of the comparator of the ratio circuit 12.

When the level of the audio signal input to this terminal becomes higher than the reference voltage of the O terminal of the comparator (&1 point in FIG. 5), a high level signal is output from the output terminal of the comparator. This signal is received by the total control circuit 19, and a high level signal 25 is sent from the terminal 24 of the control circuit 19.
A low level signal is simultaneously outputted from the analog switches 3 and 8, and the analog switch 3 is turned on and the analog switch 8 is turned off to enter the transmitting state. At this time, the high level signal at the terminal 24 causes the comparison circuit 12 to
The transistor turns on, lowering the reference voltage at the O terminal of the comparator (point b1 in FIG. 5B).

Therefore, switching does not occur even when the signal between words becomes small. At the same time, the low level signal I at terminal 25
d Ratio 4e circuit 1601' In order to turn off the run transistor, the base voltage of the comparator of the comparison circuit 16 is not high (
Point 61 in Figure 5) is designed to prevent the comparator from malfunctioning due to ambient noise, etc.

On the other hand, the amplified, rectified and smoothed audio signal input from the microphone 2 (C in FIG. 6) is sent to the comparator circuit 16 (7).
When the reference voltage of the e terminal of the comparator becomes higher (6th
Figure CcIC 2 points) Contrary to the above-described operation, an if-level signal is output from the terminal 24 of the control circuit 19, a high-level signal r'j '>J is output from the terminal 25, and the analog switch 3 is turned off. , 8 are turned on and the phone is in the receiving state. At this time, the transistor of the ratio I film circuit 12 is turned off and the reference voltage is increased (point b2 in FIG. 5B). At the same time, the transistor of the comparison circuit 16 is turned on, lowering the reference voltage (point 62 in FIG. 5, p).

In this way, by reciprocally turning on and off the transistors of comparator circuits 12 and 16, a hysteresis characteristic is provided and switching between transmitting and receiving is ensured, thereby preventing malfunctions such as speech interruptions during conversation. does not occur.

Effects of the Invention As described above, according to the present invention, the reference voltage of the comparator used in the comparison circuit is controlled by turning on and off the transistor using the switching signal of the switch in the communication direction, and the reference voltage of the comparator used in the comparison circuit is provided with hysteresis characteristics. This system ensures reliable operation of the microphone and speaker, eliminates malfunction of the audio switch due to acoustic coupling between the microphone and speaker and noise, and eliminates speech breaks during conversation.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional audio switch circuit;
3 is a block diagram of an audio switch circuit according to an embodiment of the present invention, FIG. 4 is a circuit diagram of its main parts, and FIG. 5 is a waveform diagram of its operation. 19... Control circuit, 12.14, 16.18.
... Comparison circuit, 28, 29, 30, 32. 33.
...Resistance, 31-...) Ransisk, 34...
comparator. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Ink-Hon 4-year-old test, Rio. ■ Figure 4

Claims (1)

[Claims] The input signal from the microphone is amplified, the signal is rectified and smoothed, and the output signal is connected to one input terminal of all the comparators, and the DC power supply terminal is connected to the other input terminal of the comparator via a resistor. ftsu e L, this input terminal is grounded through a resistor connected in series, and a transistor fi (D-r v lids are all connected,
The emitter is grounded, and a 11i111ql signal is applied to the base via a resistor to control all two communication directions, and the reference voltage of the comparator is changed by controlling all the transistors on and off, thereby providing full hysteresis characteristics. All q! A voice switch circuit with f characteristics.