JPS62196957A - Telephone set-loudspeaking type interphone system - Google Patents

Abstract

PURPOSE:To attain a stable calling by reducing the balance resistance of the hybrid circuit of a bidirectional amplifier with the AND output of the detection output of the direct current conducting to two telephones and keeping the balance of said hybrid circuit when two telephone sets are connected in parallel with each other. CONSTITUTION:Both telephone sets A and B switch the channel selection switches S1-S4 to the 13-14 side and at the same time have the relay connection to a loudspeaking type interphone system C in order to attain a call among three persons. Under such conditions, the direct current is conducted to both resistances 16 and 17 when the handsets of both telephones A and B are hooked off. Thus the logic levels of both detection voltage outputs 7 and 8 are set at 'H' together with the output of an AND circuit G also set at 'H'. As a result, an analog switch transistor TR3 is turned on and a resistance R19 is connected in parallel to a resistance R2. Then the parallel resistance value is halved if the resistance value of the R19 is set equal to that of the R2. Thus the same rate is attained as that of the impedance reduction caused when both telephone sets A and B are connected in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a telephone-address intercom device that can relay connect two telephones a to an audible intercom.

[Technical Background 1 of the Invention Conventionally, in this type of device, two telephones A and B are connected to channel selection switches 81.82 and 83.34, as shown in FIG.
Line 11. Connect to the +2 side so that one-way communication is possible, and connect the channel selection switch 51.32 or 83.84 to the line 13.14 (+4 is shown as ground) side. By telephone IA
, B and the loudspeaker type intercom device C, but since it is necessary to have the function of amplifying the sending and receiving signals and the simultaneous conversation function with the loudspeaker type intercom device C, the hybrid Transformer L3. 4 and amplifier A
A bidirectional amplifier consisting of I and A2 is inserted between the channel selection switch and the intercom device C.

In this case, telephones A and B shown in FIG. 2 are each constructed of the circuits shown in FIG. 3.

This circuit is known as a 601A type communication circuit, in which King is a transmitter, R is a receiver, and L5 is a guide wire ring. C
2, C3, R3, and R4 are capacitors and resistors that make up the first balanced circuit, R7 is a resistor that makes up the second balanced circuit,
VR3 and R8G are the varistors and resistors that make up the transmitting level adjustment circuit; VR2, R5, and R6 are the varistors and resistors that make up the receiving level adjusting circuit; VRl and R9 are the varistors and resistors that make up the equity noise absorption circuit. It is.

On the other hand, the loudspeaker intercom C shown in FIG. 2 is constructed of the circuit shown in FIG. 4. In the ff54 diagram, SP is a speaker and M is a condenser microphone.

L6 is a hybrid transformer, which is also used as a matching transformer for the speaker SP. CD1 is a full-wave rectifier diode for making the terminals 5 and 6 connected to the line non-polarized; R10 to R15, C5 to C7; TR1 and TR2 are resistors, capacitors, and transistors that constitute the amplifier of the capacitor microphone M; C4 is a DC blocking capacitor.

Note that a DC power source for operating this amplifier is supplied from the outside to terminals 5 and 6, as will be described later.

Returning to FIG. 2, )-131 and H82 are hook switches, and the illustrated position indicates the standby state.

Now, when you switch the selection switch 31 and 32 of Telephone IIA to the loudspeaker intercom device C side and pick up the handset,
)-Is 1 is closed and direct current is supplied to the telephone minor A from the DC power source 2 through the choke coil L2.

A signal from the transmitter T of the telephone IIA is amplified by the amplifier A1 via the hybrid transformer L3, and is output as an optical sound from the speaker SP of the loudspeaker intercom device C via the hybrid transformer L4. In this case, the output of the amplifier A1 is the secondary coil l41 of the hybrid transformer L4.
, l 42, is not input to the amplifier A2 by the bridge formed by the resistor R1 and the impedance of the loudspeaker intercom device O. On the other hand, in the loudspeaker intercom device C, the DC power supply V2 is connected to the resistor R1 and the secondary coils L41 and L of the hybrid transformer 4.
42 through the condenser microphone M shown in FIG.
DC bias is supplied to the amplifier. The signal from the microphone M of the loudspeaker intercom HlaC is amplified by the aforementioned condenser microphone amplifier, further amplified by the amplifier A2 via the hybrid transformer L4, and outputted from the handset R of the telephone set A via the hybrid transformer L3. In this case, the output from the amplifier A2 is the secondary coil l 31 of the hybrid transformer L3.
, L 32 , is not input to the amplifier A1 by the bridge formed by the resistor R2 and the impedance of the telephone IA. Note that C1 has a DC current of 131. L32
This is a capacitor for blocking the flow to R2.

The same applies to the case where the telephone 1B is relay-connected to the loudspeaker intercom device CC.

In this way, call 1! The signal A or B and the signal from the loudspeaker intercom device C are mutually amplified by a bidirectional amplifier and transmitted to the other party's device.

[Problems with the Background Art] However, in the conventional device described above, when telephones A and B are simultaneously relay-connected to the loudspeaker intercom device C for the purpose of three-party communication, it is necessary to balance the resistance R2 of the hybrid transformer L3. Since the impedance of the telephone was reduced by half, the balance of the bridge was lost, causing the bidirectional amplifier to oscillate. In addition, to prevent oscillation even if the bridge becomes unbalanced, the amplifier AI,
It is conceivable to lower the amplification degree of A2, but in this case there is a drawback that the speech level will be lowered.

[Object of the Invention] The present invention eliminates the above-mentioned drawbacks, and provides a telephone that can prevent the bidirectional amplifier from oscillating without reducing the speech level even when two telephones are relay-connected to a loudspeaker interbon device at the same time. - An object of the present invention is to provide a loudspeaker intercom device.

[Summary of the Invention] In this invention, detection means for detecting the direct current flowing through each telephone n when each telephone selects the loudspeaker intercom device side is provided, and the detection outputs of the two detection means are used to generate a bidirectional amplifier. By lowering the balance resistance of the no-even 1-knot circuit, the purpose stated in - is quickly achieved.

[Embodiment of the Invention] FIG. 1 shows an embodiment of the present invention, and the same parts as in FIG. 2 are given the same symbols.

In Figure 1, Sl and S2 are telephones! FIA tuning switch, 83.84 is Telephone II B tuning switch, 1
1 and 2 are lines for communicating with the loudspeaker intercom device C.

H81 and H82 are phone 1! A, B hook switch, V
1. V 2 is a DC power supply, 11.12 is each 11-1
2. +3-14 (however, 14 is shown as ground) is a choke coil for supplying direct current to the line. E is a bidirectional amplifier, and a hybrid transformer L3. L4, amplifiers A1 and A2, and balancing resistors R1 and R2, and further includes a resistor R
1 connected in parallel with 2 (includes a lance correction resistor R19 and an analog switch transistor TR3. R1
6, R17 is a phone IF! Telephones A and B1 when A and B are respectively relay-connected to the loudspeaker intercom. :Resistor to detect the flowing DC current, C8 and C9 are R for the audio signal.
This is a bypass capacitor for bypassing R16 and R17.

The detection type pressure cuffs 8 of the resistors R16 and R17 are each connected to the input of the AND circuit G, and the output of the AND circuit G is connected via the resistor R18 to the analog switch transistor T.
Connected to the base of R3. Lightning speech A and B are S
1. S2 and S3. S 4 11-12
If you switch to the side and pick up the handset, you can make one-to-one calls. Also, when relaying only the telephone flA to the loudspeaker intercom device C, S1. S 2 to 1
When I switched to the 3-14 side and picked up the handset, the phone number 11
DC current is supplied to A from the DC power source 2 through the choke coil L2, and communication with the loudspeaker intercom device C is possible through the bidirectional amplifier E. At this time, resistance R
Since a DC current flows through resistor R16, the logic level of the detection type pressure cuff of resistor R16 becomes "H". However, resistor R1
Since no direct current is flowing through the resistor R17, the logic level of the detected voltage output 8 of the resistor R17 becomes L'''.

Therefore, the output of the AND circuit G becomes 'L', the transistor TR3 is turned off, and the balance resistance of the hybrid transformer L3 becomes only R2, maintaining the balance with the impedance of the telephone 11A.Similarly, only the telephone 1B is connected to the loudspeaker intercom. Even when relaying connection to device C, the balance resistor is only R2 to maintain balance with the impedance of telephone B.

However, telephones A and B use the channel selection switch S1 for the purpose of making a call. S2. and S3. S 4 13
-1 Switch to side 4 and at the same time loudspeaker intercom device C
If you pick up both handsets when relaying the connection to
Since a DC current flows through both resistors R16 and R17, the logic levels of the detection type pressure cuff 8 are both '+1', and the output of the AND circuit G becomes 'H'. Therefore, the analog switch transistor TR3 is turned on, and the resistor R19 is connected in parallel to the resistor R2. Therefore, R1
If the 1-wire resistor of 9 is set to the same 1-wire resistor as R2, the parallel resistance value will be 1/2.

As a result, the impedance decreases at the same rate as when the telephone vMA and B are connected in parallel, the bridge balance of the hybrid transformer is not disrupted, and the bidirectional amplifier does not increase the optical oscillation by +5, and the margin for oscillation is reduced. There is no decline.

[Effects of the Invention] As explained above, in this Komei, when connecting two telephones to a loudspeaker intercom device, the direct current flowing through each telephone ■ is detected when telephone n is relay-connected to the loudspeaker intercom device. The balance resistance of the hybrid circuit of the bidirectional amplifier is lowered by the AND output of the two detection outputs, and the telephone is configured to maintain the balance of the hybrid circuit when two phones are connected in parallel.
Even when a three-party call is made between two telephones and a loudspeaker intercom device, the two-way amplifier no longer vibrates.
It has the advantage of being able to make stable calls.

Furthermore, since the direct current flowing through the telephone is directly detected, there is an advantage that the balance of the hybrid circuit will not be disrupted even if the telephone becomes disconnected for some reason.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram of a conventional telephone-address type intercom device, Fig. 3 is a communication circuit diagram of a telephone, and Fig. 4 is a circuit diagram of a conventional telephone-address type intercom device. It is a circuit diagram. A, B... Telephone 1, C... Loudspeaker intercom device, A I, A2... Amplifier, E... Bidirectional amplifier, R16°R17... Resistor, G... Logic Product circuit, TR3...transistor. Figure 4

Claims (1)

[Claims] It has two telephones that communicate with each other using handsets, a loudspeaker intercom device common to these telephones, and a bidirectional amplifier equipped with a hybrid circuit that relays the telephone to the loudspeaker intercom device. In a telephone-address type intercom device, each telephone is provided with detection means for detecting the direct current flowing through the telephone relay-connected to the intercom device, and the detection outputs of these two detection means are used to detect the bidirectional amplifier. A telephone-address type intercom device characterized by lowering the balance resistance of a hybrid circuit.