JPH1075316A - Interphone set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the interphone set in which variation in an output impedance toward a 2-way amplifier is small due to line changeover control by a slave set line changeover circuit. SOLUTION: The interphone set is provided with a plurality of slave sets 20 and a master set connecting to each slave set 20 via a 2-way amplifier 11 and a slave set line changeover circuit 12 through slave set lines L11, L12. In this case, the slave set line changeover circuit 12 connects an output amplifier of the 2-way amplifier 11 in a direction of the slave set and each slave set 20 via switching diodes D1, D2 and conduction of the switching diodes D1, D2 is controlled, based on a bias applied to the slave set lines L11, L12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an intercom apparatus, and more particularly, to an intercom apparatus having a plurality of slave units.

[0002]

2. Description of the Related Art Conventionally, in an intercom apparatus including a plurality of slave units and a master unit connected to the slave units via respective slave unit lines, as shown in FIG. Are connected to the base unit 10 via respective slave unit lines L11, L12,.
When the sub-base unit 30 is provided, the base unit 10 and the sub-base unit 30
Are connected by an extension communication line L2 which is a transmission line. Specifically, as shown in FIG.
Are connected via the slave units L11, L12,... Through the bidirectional amplifier 11 and the slave unit line switching circuit 16 for making a call with the master unit 10 via the slave unit 20. In the following, this slave unit line will be described by exemplifying a configuration having two lines, but the present invention is not limited to this.

[0003] In addition to the above-described bidirectional amplifier 11 and slave unit line switching circuit 16, master unit 10 includes a slave unit 2 as shown in FIG.
A handset 13 having a speaker and a microphone for communicating with the telephone set 0 and the sub master unit 30; a two-wire / four-wire conversion circuit 14 for transmitting / receiving audio signals to / from the handset 13;

[0004] The bidirectional amplifier 11 is for amplifying an audio signal transmitted to and received from the slave unit 20 to a level that allows communication. The bidirectional amplifier 11 is generally configured with a bridge circuit at both ends thereof, separates an input audio signal in each direction, and separates the separated audio signal into an operational amplifier for transmission to a slave unit 20. After being amplified by a receiving amplifier 112 (not described in detail) constituted by 111 and a differential amplifier, a two-way audio signal is amplified by two-line output again.

[0005] The operational amplifier 111 has a
In order to prevent the voice signal of the transmission to the handset 20 from being transmitted to the reception amplifier 112 side, the impedance of the handset side as viewed from the resistor R16, the reception amplifier 112, and the resistor R1
6. The resistor R17 and the balancing network BN are bridge-connected, and the impedance of the balancing network BN is adjusted to a predetermined value to reduce the wraparound of the input audio signal. And the resistance R
i, the gain is increased by the resistor Rf, the resistor R18, the resistor R1.
9, the output bias is set to a predetermined value, and the resistance R16 is set to a predetermined value.

The above-described bidirectional amplifier 11 does not oscillate each amplifier due to fluctuations in the line impedance of the respective communication circuits connected to both ends. A CPU (not shown) is operated so that each amplifier operates via the switching circuit 16.
Power supply is controlled by such control means. In addition,
Most of the above balancing network BN is formed by a resistance element.

[0007] The slave unit line switching circuit 16 includes a plurality of slave units 20.
Of the slave units L11 and L12 in order to conduct a call with a predetermined slave unit among the slave units. Via a voltage dividing circuit, a predetermined operating voltage is applied to each of the slave unit lines L11 and L1.
2, a switching element Q1 such as a transistor for controlling the application
Q2, diodes D3 and D4 for operating the bidirectional amplifier 11 by applying the voltage,
A resistor R1 for applying a standby voltage which is a bias at the time of standby
4. Analog switches SW1 and SW for line switching connection controlled by a resistor R15 and a CPU (not shown)
And 2. The voltage value during standby is, for example, about 1 to 2 V, and is used to transmit a calling signal from the handset 20 when a call switch (not shown) is pressed, and is built in the handset 20. The value is set so that the microphone amplifier does not operate.

The two-wire / four-wire conversion circuit 14 is used for the handset 1
This is for transmitting the transmission / reception signal of the voice to / from the terminal 3 by two lines. In this device, a differential amplifier for amplifying the voice signal of the reception to the speaker of the handset 13 and the transmission from the microphone of the handset 13 are used. It has an operational amplifier and the like for amplifying the voice signal of the talk.

The communication line switching circuit 15 is for making a call between desired devices in each connected device. For example, when a predetermined handset 20 and the base unit 10 make a call, the sub-base unit The CPU (not shown) controls the opening and closing so that only those of the base unit 20 become conductive without conducting.

The handset 20 is the same as a generally known handset, and a description thereof will be omitted. The sub-parent device 30 is
A handset 31 having a speaker and a microphone for talking with the base unit 10, a two-wire / four-wire conversion circuit 32 for transmitting and receiving audio signals to and from the handset 31, and a communication line switching circuit 33. That is, the sub-base unit 30 receives the bi-directional amplifier 11 and the slave unit line switching circuit 16 from the base unit 10.
Has been removed.

The operation of the intercom apparatus described above is as follows. In a standby state, when a call switch (not shown) of the handset 20 is pressed, a call sound signal is output from a call sound circuit (not shown) of the base unit 10 to the extension line L2. Output to
A ringing tone is emitted from the speakers of the handset 13 and the handset 31 of the base unit 10, the sub-base unit 30, and the like. When the handset 13 of the base unit 10 is picked up, the base unit 1
The communication line switching circuit 15 is turned on by the CPU 0, and only the two-wire / four-wire conversion circuit 14 is connected to the two-way amplifier 11 for communication. At this time, the communication line switching circuit 3 of the sub master unit 30
3 is not conducted, and communication between the master unit 10 and the slave unit 20 is enabled.

Further, in place of the above-mentioned base unit 10, sub-base unit 3
If the handset 31 of 0 is picked up,
0 makes the communication line switching circuit 33 conductive,
The call is connected to the bidirectional amplifier 11. And the parent machine 10
Is not conducted, and a call between the sub master unit 30 and the slave unit 20 becomes possible. When making an extension call, for example, only the communication line switching circuit 15 of the base unit 10 and the communication line switching circuit 33 of the sub-base unit 30 are turned on, and a call between the base unit 10 and the sub-base unit 30 is possible. Becomes At this time, the bidirectional amplifier 11 is controlled so as not to operate.

[0013]

By the way, the bridge circuit of the input stage on the side of the slave unit lines L11 and L12 of the bidirectional amplifier 11 is composed of the bidirectional amplifier 11 and the slave unit line L11.
Line impedance fluctuations at the connection to L12 may cause oscillation phenomena due to reflection of audio signals. The analog switch used in the slave unit line switching circuit 16 has a large on-resistance when conducting. As a result, the output amplifier 111 oscillates, howling, etc., due to variations in the on-resistance of the analog switches Sw1 and Sw2 inserted in series with the slave lines L11, L12 and variations in the impedance of the wiring of the slave lines L11, L12. And the sound quality of the call varied greatly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to reduce the fluctuation of output impedance toward a bidirectional amplifier by line switching control by a slave unit line switching circuit. Another object of the present invention is to provide an intercom apparatus with less variation in call sound quality.

[0015]

In order to achieve the above object, an intercom apparatus according to claim 1 has at least two components.
One slave unit, and a master unit connected to the slave unit via each slave unit line via a bidirectional amplifier and a slave unit line switching circuit,
In the intercom apparatus provided with, the slave unit line switching circuit connects the output amplifier in the slave unit direction of the bidirectional amplifier to each slave unit via a switching diode, and applies a voltage to each slave unit line. , The conduction of the switching diode is controlled by the bias of the switching diode. As a result, the slave unit line switching circuit performs line control with low conduction impedance.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an intercom apparatus according to the present invention will be described below with reference to FIGS. In the present embodiment, components denoted by the same reference numerals as those described as the conventional example are substantially the same, and detailed description is omitted.

FIG. 1 is a circuit diagram of a slave unit line switching circuit of an intercom apparatus. This intercom apparatus also includes a master unit 10, slave units 20 and 20 connected to master unit 10 by slave unit lines L11 and L12, and a secondary master unit 30 connected to master unit 10 and extension line L2. ing.

Base unit 10 has a bidirectional amplifier 11, a handset line switching circuit 12, a handset 13, a two-wire / four-wire conversion circuit 14, and a communication line switching circuit 15, as in the conventional example. .

The sub-unit line switching circuit 12 controls the conduction of the sub-unit lines L11 and L12 when making a call with a predetermined sub-unit of the plurality of sub-units 20.
Diodes D1 and D as switching diodes are provided between the operational amplifier 111 corresponding to the output amplifier of the bidirectional amplifier 11 in the direction toward the slave 20 and the slaves 20 and 20.
2, and the conduction of the diodes D1 and D2 is controlled by a bias generated by applying a voltage to each slave unit line.

The diodes D1 and D2 have cathodes at the output terminals of the bidirectional amplifier 11 on the side of the slave unit 20, and anodes at the switching elements Q such as transistors from a CPU or the like.
1, a resistor R10 and a resistor R by a conduction control signal to Q2.
Slave unit line L1 to which a predetermined operating voltage is applied by a voltage dividing circuit of power supply Vcc by a resistor 11 and resistors R12 and R13.
1 and L12, respectively.
The power supply Vcc is applied to the slave unit lines L11 and L12 in order to apply a standby voltage which is a bias during standby of the slave units 20 and 20.
Are connected to a resistor R14 and a resistor R15. In addition,
The capacitor C1 is a coupling capacitor for DC separation between the bidirectional amplifier 11 and the slave unit line switching circuit 12, and the capacitor C2 is a decoupling capacitor for stabilizing the voltage of the power supply Vcc.

In the above configuration, the resistance R18 and the resistance R1 of the operational amplifier 111 of the bidirectional amplifier 11 are
9, the relationship between the applied voltage Vw at the time of standby to each slave unit line in the slave unit line switching circuit 12 and the applied voltage Vt at the time of communication with the slave units 20 and 20 is represented by a diode. D1, diode D
2 is Vf, Vw <Vo <(Vt
−Vf).

Next, the operation of the above-described intercom apparatus for connecting an extension communication line in a standby mode, a slave unit communication and an extension communication will be described.

[Standby] In a stand-by state in which the master unit 10, the slave unit 20 and the auxiliary master unit 30 are not in a call, the switching elements Q1, Q2 are sent from the CPU of the master unit 10.
A high-level voltage is input to the base of. Then, the switching elements Q1 and Q2 are turned off, and the DC voltages as standby voltages are respectively supplied to the slave unit lines L11 and L12 of the intercom slave units A and B as the slave units 20 and 20 via the resistors R14 and R15. Vw is supplied. At this time, the bidirectional amplifier 11 is controlled so that the power supply voltage is not applied and does not operate.

[During a Call] When a call is being made between the base unit 10 or the sub-base unit 30 and the intercom slave unit A, which is the slave unit 20, the CPU of the master unit 10 sends a signal to the base of the switch element Q1. Are configured to be turned on when a low level voltage is input. As a result, the power supply voltage is applied to the operational amplifier 111 via the diode D3, and the bidirectional amplifier 11 enters an operating state. At this time, the power supply Vcc is applied to the non-inverting input terminal of the operational amplifier 111.
Is applied with a voltage divided by the resistor R18 and the resistor R19, the output voltage Vo is the voltage V + output as a DC bias voltage.

At this time, the intercom slave A is connected to the resistor R1 by the conduction of the switch element Q1.
The DC voltage is also applied to the slave unit line L11 through 0. This applied voltage is the communication voltage Vt, which is almost equal to the power supply Vcc.
Is determined by a voltage dividing ratio obtained by dividing the voltage by the resistors R10 and R11. The applied voltage Vt is, for example, approximately 6 V, and is set to a value at which a microphone amplifier or the like built in the slave unit 20 can operate. At this time, the voltage applied to the slave unit line L12 toward the intercom slave unit B remains at the standby voltage Vw because the switch element Q2 is in a non-conductive state.

At the time of this call, the relationship between the output voltage Vo of the operational amplifier 111 and the voltage applied to each of the slave unit lines L11 and L12 is Vw <Vo <(Vt-Vf), and the diode D1 goes forward. The direction and the diode D2 are respectively biased in the reverse direction, so that only the intercom slave A among the slaves 20 can talk with the master unit 10 or the auxiliary master unit 30. At this time, the voltage applied to the slave unit line L12 is maintained at the standby voltage Vw because the diode D4 is biased in the reverse direction and turned off. In the above-described configuration, when a call is performed by the intercom slave unit B, the conduction control of the switch elements Q1 and Q2 is reversed.

When the diode is used as a switching diode of an audio circuit such as a speech line switching circuit as in the case of the diodes D1 and D2, the AC impedance in a state where the DC bias is applied in the forward direction is the same as that of a conventional analog switch. It is approximately 1/10 compared to the case of. Therefore, the line switching control by the slave unit line switching circuit reduces the variation of the output impedance toward the bidirectional amplifier, and the influence of the variation of the impedance matching can be reduced. In addition, a commonly used analog switch has a withstand voltage of about 15 V, and the switching diodes D1 and D2 used in the above configuration have a withstand voltage of about 40 to 50 V and use voltage about three times as high. Since the range can be set, by setting the voltage applied to the slave unit line toward the slave unit 20 so as to increase the amplitude of the audio signal, it is possible to improve the call sound quality.

According to the intercom apparatus described above,
Since the slave unit line switching circuit 12 controls the lines of the slave unit lines L11 and L12 with a low conduction impedance, the output impedance toward the bidirectional amplifier is reduced by the line switching control by the slave unit line switching circuit. Thus, it is possible to reduce variation in call sound quality.
In addition, since the switching diode is switched by controlling the voltage applied to the slave unit line, a special circuit for controlling conduction is not required, and the slave unit line switching circuit is lower in cost than a conventional analog switch. Can be realized.

[0029]

According to the first aspect of the present invention, since the slave unit line switching circuit controls the line with a low conduction impedance, the output to the bidirectional amplifier is performed by the line switching control by the slave unit line switching circuit. The variation in impedance is small, and thus, the variation in speech sound quality can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a slave unit line switching circuit showing one embodiment of an intercom apparatus of the present invention.

FIG. 2 is a configuration diagram of the intercom apparatus shown in FIG.

FIG. 3 is a circuit configuration diagram of a slave unit line switching circuit of a conventional intercom apparatus.

FIG. 4 is a configuration diagram of a conventional intercom apparatus.

[Explanation of symbols]

 Reference Signs List 10 master unit 11 bidirectional amplifier 111 operational amplifier (output amplifier) 12 slave unit line switching circuit 20 slave unit D1, D2 diode (switching diode) L11, L12 slave unit line L2 extension line

Claims (1)

[Claims] 1. An intercom apparatus comprising: at least two slave units; and a master unit connected to the slave units via respective slave unit lines via a bidirectional amplifier and a slave unit line switching circuit. The machine line switching circuit connects the output amplifier in the slave unit direction of the bidirectional amplifier to each slave unit via a switching diode, and controls the conduction of the switching diode by applying a voltage to each slave unit line. An intercom device.