JPS62196956A - Telephone set-loudspeaking type interphone system - Google Patents

Abstract

PURPOSE:To increase the speech sending level to a loudspeaking type interphone system by using the output of a comparator to change the amplification degree of a bidirectional amplifier in both directions opposite to each other. CONSTITUTION:The reference voltage REF2 of a comparator CMP2 is set lower than the reference voltage REF1 of a comparator CMP1. Thus the output of the CMP2 is inverted by the voltage v4 lower than the voltage v2 shown in the diagram. Then a TR4 is turned off and the amplification degree is lowered down to G3 from G4. Then the amplification degree rises up to G4 from G3 with the voltage v3 lower than the voltage v1 shown in the diagram. Here the REF1 of the CMP1 is set so that the v2 is equal to a normal speech sending level of a telephone A. At the time of calling from the telephone A, the amplification degree rises up by g1, therefore, the loudspeaking level is increased through a speaker SP of a loudspeaking type interphone system B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a telephone-address intercom device capable of relay-connecting a telephone (1) to an audible intercom.

[Technical Background of the Invention] Conventionally, this type of device has been used as a telephone IA as shown in FIG.
A channel selection switch S1 for selectively switching and connecting telephone A to the central office line side and the intercom apparatus side in order to make an outside line call and also to make a call with intercom apparatus B.
．． S2 is provided, and the 32N station switch 81.32 is connected to the central office lines 5 and 6 to make an outside call, and conversely, it is connected to the lines 7 and 8 on the intercom device B side to make a call to the intercom device B. However, since it is necessary to transmit calls to the loudspeaker intercom, amplify the received signal, and make simultaneous calls, a channel selection switch and intercom equipment are required. Generally, a hybrid transformer L2. A bidirectional amplifier constituted by L3 and amplifiers A1 and A2 is inserted.

In this case, the telephone t,'IA is constructed with the circuit shown in FIG. In the figure, the dial circuit and tone ring circuit are omitted because they are not directly related to the present invention.

This circuit is known as a 601A type communication circuit, where T is a transmitter, R is a receiver, and L4 is a guide ring. C2, C3, R3, and R4 are capacitors and resistors that make up the first balanced circuit network; R7 is a resistor that makes up the second balanced circuit; VR3 and R8 are varistors and resistors that make up the transmitting level adjustment circuit; VR2 and Re , R5 are a varistor and a resistor constituting the receiving level adjustment circuit, VRl, R
Reference numeral 9 denotes a varistor and a resistor that constitute an impulsive noise absorption circuit.

On the other hand, the loudspeaker intercom B shown in FIG. 4 is constructed of the circuit shown in FIG. In the same figure, SP is a speaker,
M is a capacitor microbond, and L5 is a hybrid transformer, which is also used here as a matching transformer for the speaker SP.

CD I is a full-wave rectifier diode for non-polarizing terminals 3 and 4 connected to the line, R10~R15°C5~
C7, TR1, and TR2 are a resistor, a capacitor, and a one-herald transistor that constitute the amplifier of the condenser microphone.

C4 is a DC blocking capacitor. In this case, DC power for operating the amplifier is supplied from the outside to the terminals 3 and 4, as will be described later.

Returning to FIG. 4, H8 is a hook switch, and the illustrated position indicates a special state. Now, select channel S
1. Connect S2 to the loudspeaker intercom device B as shown.
When the telephone wires 7 and 8 are switched to 8 and the handset is picked up, the hook switch H8 is closed, and direct current is supplied to the telephone 41A from the direct current power supply VC through the choke coil L1. The signal from the transmitter T of the telephone mA is transmitted through the hybrid transformer L.
2, the signal is amplified by the amplifier A1, and is output from the speaker SP of the loudspeaker intercom device ffB through the hybrid transformer L3. In this case, the output of the amplifier A1 is the secondary coil L31 of the hybrid transformer L3.
．． 132. Due to the bridge formed by the resistor R2 and the impedance of the loudspeaker intercom system @B, the signal is not input to the amplifier A2. Loudspeaker intercom device B
In 31., from the DC power supply VC to R2, the secondary coil of the hybrid transformer L3. Through the capacitor 32, a DC bias is supplied to the condenser microphone amplifier shown in FIG. The signal from the microphone M of the loudspeaker intercom system "aB" is amplified by the aforementioned capacitor microphone amplifier, passed through the hybrid transformer L3, and then amplified by the amplifier A2.
Call I through 2! The sound is generated from the receiver R of the IA. In this case, the output from the amplifier A2 is the secondary coil L21°L22. of the hybrid transformer L2. Due to the bridging formed by resistor RIJ5 and the impedance of the telephone mA, there is no input to amplifier A1. Note that C1 is a capacitor for blocking direct current from flowing to R1.

In this way, the signal from telephone A and the signal from loudspeaker intercom device B are transmitted to bidirectional amplifier C, which consists of amplifiers A1 and A2.
The signals are amplified and transmitted to the other device.

[Problems in the background art] However, in the above conventional device, the hybrid transformer L
In order to prevent the balance of 2.13 from being distorted due to the influence of line resistance and phase rotation due to frequency, and to prevent positive feedback from oscillating, amplify 'aA+.

The amplification degree of A2 is set low. Therefore, there was a problem in that the speech level was low. Furthermore, amplification i! !
Since the amplification degrees of 1iA1 and A2 are fixed, there is a problem in that the sidetone of the telephone flA caused by the acoustic coupling between the speaker SP of the amplified intercom 8taB and the microphone M is large compared to the speech level.

[Object of the Invention] The present invention eliminates the above-mentioned drawbacks, can increase the speech level, does not worsen the sidetone of the telephone due to acoustic coupling even if the speech level is increased, and has improved simultaneous speech performance. It is an object of the present invention to provide a telephone-address type intercom device that does not deteriorate.

[Summary of the Invention] The present invention includes a detection circuit that detects a transmission signal to a loudspeaker intercom device, two comparators that respond to the output of the detection circuit, and an amplification degree of, for example, 1 for the output of the comparator.
Two amplifiers that vary within a range of 0 dB or less are provided as bidirectional amplifiers, and the amplification of these amplifiers is varied in opposite directions depending on the level of speech sent to the loudspeaker intercom device, and the amplification of the receiving amplifier is The above object is achieved by configuring the structure such that the change occurs at a detection level lower than the detection level at which the amplification change of the transmitting amplifier occurs.

[Embodiment of the Invention] FIG. 1 shows an embodiment of the present invention, and the same parts as in FIG. 4 are given the same symbols.

In FIG. 1, 5 and 6 are central lines, S1. S2 is a tuning switch, L1 is a choke coil for DC voltage supply, L2 is a hybrid transformer, C1 is a DC blocking capacitor, and R1 is a balancing resistor.

Reference numeral A is a telephone, which is constructed with the communication circuit shown in FIG.

A5 is a transmitting amplifier, and is configured so that the degree of amplification can be varied by a resistor. In this case, the resistor R22
, R21 are connected in series, and the degree of amplification is changed by turning on and off an analog switch transistor TR3 connected in parallel with the resistor R21. In other words, when TR3 is turned on, the amplification degree of A5 changes from G1 to G2.
The amplification degree change width Q 1 (=G 2 - G 1)
The value of the resistor R222 is set so that the value is 10 dB or less, preferably 6 to 7 dB. L3 is a hybrid transformer, and R2 is a balancing resistor.

Reference numeral B denotes a loudspeaker intercom device, which is composed of the circuit shown in FIG. 80 is a receiving amplifier, and like the transmitting amplifier A5, the degree of amplification can be varied by changing the resistance.Resistors R20 and R19 are connected in series, and an analog switch is connected in parallel with the resistor R19. transistor TR4
The configuration is such that the degree of amplification changes depending on whether it is turned on or off. In other words, when TR4 is turned on, the amplification degree of 80 becomes 0.
3 to 04, and the amplification degree change width Q 2 (=G 4-
The values of resistors R20 and R19 are set so that G3) has the same value or more as g1 in A5. C8,R
16, CD 2. CD 3. C9 and R17 are a capacitor, a resistor, and a diode that constitute the detection circuit E, which detects the transmission signal V2 generated at the terminal 3 of the loudspeaker intercom device B.

The output V3 of the detection circuit E is input to the non-inverting input of the comparator CMP1 and the inverting input of CMP2.

The inverting input of comparator CMP 1 has a reference voltage RE
F 1 is applied. Therefore, when the output voltage V3 of the detection circuit E exceeds the reference voltage REF1, the output of the comparator CMP2 becomes "H" level, and TR3 is turned on through R23.
A base 2% 7u pressure REF2 is applied to the non-inverting input of No.2.

Therefore, the output voltage ■3 of the detection circuit E is the reference voltage REF.
When the value exceeds 2, the output of the comparator CMP2 becomes a "yes" level, and TR4 is turned off. Here, the reference voltage RE
F2 is set smaller than the reference voltage REF1. With this configuration, the transmitting signal V of telephone A
1 (input signal of A5) has a characteristic as shown in FIG. That is, when (1) increases from O and reaches the voltage V2 determined by the initial amplification G1 of the amplifier A5, the detection circuit E and the reference voltage REF1, TR3 is turned on and the amplification increases from G1 to G2. Amplification degree is G
When the voltage rises to 2, even if Vl is constant, V2 rises and positive feedback occurs, so hysteresis occurs as shown in the figure.
■When 1 falls, TR3 turns off when it reaches the voltage V1 determined by the amplification change ec+1, and the amplification becomes G2.
From there, it descends to G1.

Here, in addition to the transmission signal V2 to the loudspeaker intercom device B, the terminal 3 receives a transmission signal from the microphone M of the loudspeaker intercom device ff1B and the hybrid transformer L2.
．． A sidetone signal is generated due to the imbalance of L3, but this signal level is extremely small compared to the transmitting signal level V2, so the operation of comparators CMP1 and CMP2 is almost determined by the transmitting signal ■1 of the telephone. You can think about it.

On the other hand, the change in the amplification degree for the signal V1 of 〇 to the amplifier is
The above-mentioned amplifier A5, detection circuit E, and comparator CMP1
It is passively determined by the change in V3 determined by the positive feedback loop, and the characteristics are as shown in FIG. That is, since the reference voltage REF2 of the comparator CMP2 is set lower than the reference voltage REF1 of the comparator CMP1, the output of the comparator CMP2 is inverted at voltage 4 lower than V2 in FIG. 2, and TR4 is turned off. The amplification degree decreases from G4 to G3. Then, the amplification degree increases from G3 to G4 at a voltage V3 lower than 1 in FIG. In addition,
The reference voltage REF1 of the comparator CMP1 is set at v2 in FIG. 2 to have a value corresponding to the normal transmission level in the telephone IA.

With this configuration, when transmitting a call from telephone II A, only the amplification degree of amplifier A5 increases by 91, so that speaker SP of loudspeaker intercom device B increases.
The level of sound produced increases. However, amplifier A5
When the amplification degree of 6 has increased by 91, the amplification degree of 6 to the amplifier has already decreased by g2, which is the same as 91 or more. sidetones due to acoustic coupling are not worsened. In addition, loudspeaker intercom device B
When receiving a call from , the amplification degree of 〇 to the amplifier is increased, so the receiving level does not drop.

As is clear from FIGS. 2 and 3, a situation where the amplification degree of amplifier A5 increases to G2 and at the same time the amplification degree of amplifier A6 increases to G4 cannot occur, compared to the conventional example. , the margin against oscillation does not deteriorate4.
When telephone A and loudspeaker intercom device B transmit at the same time, the voice level of loudspeaker intercom device HB is g.
However, since g2 is set to about 10 dB, there is no problem in normal conversation without significantly impairing simultaneous conversation performance.

[Effects of the Invention] As explained above, according to the present invention, when a telephone communication circuit is relay-connected to a loudspeaker intercom device, two hybrid circuits and two variable amplification type amplifiers are connected between the two. Furthermore, a detection circuit for detecting the transmission signal to the loudspeaker intercom device and two comparators responsive to the output thereof are provided, and the outputs of these comparators mutually adjust the amplification degrees of the bidirectional amplifiers. Because it is configured to change in the opposite direction, it is possible to increase the level of speech sent to the loudspeaker intercom device, and it does not worsen the sidetone caused by the sound tube coupling between the speaker and microphone of the loudspeaker intercom device, and allows simultaneous calls. This has the advantage that the performance is not significantly impaired and the margin against oscillation of the bidirectional amplifier is not deteriorated.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the device of the present invention, Fig. 2 is a characteristic diagram of amplifier A5, Fig. 3 is a characteristic diagram of amplifier A5, and Fig. 4 is a circuit diagram of a conventional telephone-address intercom device. Figure, 5th
The figure is a telephone call circuit diagram, and FIG. 6 is a circuit diagram of a loudspeaker intercom. A: Telephone, B: Loudspeaker intercom device, A
5, A6...variable amplification amplifier, CMP 1. C
MP2... Comparator, D... Bidirectional amplifier, E
...detection circuit, TR3, TR4...1 to transistor, L2゜L3... hybrid transformer. o V3 V4 Figure 6

Claims (2)

[Claims] (1) Two hybrid circuits and two variable amplification amplifiers inserted between the telephone communication circuit and the loudspeaker intercom device, and a detection circuit that detects the level of the signal sent to the loudspeaker intercom device. and two comparators that vary the amplification degrees of the two amplifiers in response to the output of the detection circuit. (2) The amplification change width of the two amplifiers shall be 10 dB or less, and the two comparators will change the amplification in opposite directions, and the amplification change of the amplifier for receiving calls on the telephone will be equal to that for sending calls. 2. The telephone-address type intercom device according to claim 1, wherein the threshold levels of the two comparators are set so that the amplification change of the amplifier occurs at a detection level lower than the detection level at which the change occurs.