JPS6182564A - Power receiving circuit in inter-office relay - Google Patents

Abstract

PURPOSE:To decrease power consumption of the power receiving circuit by impressing a constant voltage between a collector of Tr connected to the inter- office trunk and a base, lowering an alternating impedance between the base and the emitter and giving a constant voltage power receiving characteristic, which is not influenced by the alternating current, to Tr. CONSTITUTION:A direct current voltage is supplied from a terminal 1 of the power receiving circuit through a resistance 16 and a Zener diode 17 to a Tr 19 base. A base electric current of Tr 19 minute, and consequently, a voltage between a collector of Tr and a base becomes equal to a Zener voltage. Consequently, a remaining voltage between terminals 1 and 2 of the power receiving circuit is also constant and a constant voltage power receiving characteristic is shown. An electric current, which flows through Tr 19 and 20, returns from the terminal 2 through a contact 3 for a dial transmission to the direct current power source and forms a loop electric current. Since a capacitor 18 by-passes the signal of a voice, etc., and the resistance 16 and a base voltage of Tr 19 will not be changed, Tr 19 and 20 form high impedance in an alternating current manner.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a DC loop type power receiving circuit that constitutes an inter-office relay line of an exchange, and in particular to a power receiving circuit that realizes constant voltage power receiving characteristics using a semi-flexible body. Regarding circuits.

An exchange not only performs exchange between subscribers connected to the exchange, but also performs relay between exchanges to exchange between subscribers of different exchanges. This relaying between exchanges requires a DC loop type power receiving circuit for the interoffice relay line as well as the power receiving circuit for the subscriber line.

A plurality of power receiving circuits for interoffice relaying provided in an exchange are usually mounted at the same location due to equipment configuration considerations. Therefore, there is a strong demand for miniaturization of power receiving circuits, and reducing power consumption is an important factor for this purpose.

[Conventional technology]

Conventional power receiving circuits include methods using coils and methods consisting of electronic circuits, but both have constant resistance power receiving characteristics.
When power consumption reaches 0.5 to 1.5H and a large number of circuits are grouped together, heat is generated.

FIG. 3 shows an example of a power receiving circuit using a conventional coil.

The DC current supplied from the DC power supply 11 of the opposing exchange via the dial pulse relay relay 10 and the relay line 15 is passed from the terminal 1 through the contact 4 of the power receiving circuit 8 to the equivalent inductance 6 of the coil 5 and the equivalent resistance. 7, from the terminal 2 to the relay line 14 and the relay 10.
Return to

The contact 3 of the power receiving circuit 8 is a contact for dial transmission, and is used when transferring the dial to the opposite exchange.During dialing, the contact 4 is open and the coil 5 is connected to the relay line 14.15.
be separated from

Signals such as audio sent from the terminal 4WS to the relay port vA14゜15 via the 2-wire/4-wire conversion circuit 13 and the DC blocking capacitor 12 are not attenuated by the coil 5, and are passed through the DC blocking capacitor of the opposing exchange. 9 and then transferred to the opposite exchange.

The signal transferred from the opposite exchange passes through a capacitor 9, a trunk line 14, 15 and a capacitor 12, enters a 2-wire/4VA conversion circuit 13, and is sent to a terminal 4WR.

Normally, the DC resistance of the relay 10 is about 400Ω, and the equivalent resistance 7 of the coil 5 of the power receiving circuit 8 is about 100 to 500Ω. Therefore, if the line resistance of the relay lines 14 and 15 is almost zero, the power consumption generated by the equivalent resistance 7 is at most 1.5
It reaches about W.

[Problem that the invention seeks to solve]

The above-described power receiving circuit having constant resistance power receiving characteristics generates a large amount of heat, and the temperature of a device in which a large number of power receiving circuits are mounted increases, making it difficult to miniaturize the device.

[Means for solving problems]

The above problem can be solved by providing means for keeping the DC voltage between the collector and base of the transistor at a constant value and means for lowering the AC impedance between the base and emitter of the transistor, so that the signal superimposed on the inter-office relay line is This can be solved by having a constant voltage receiving characteristic regardless of the voltage.

[Effect]

In other words, a constant voltage is applied between the collector and base of the transistor connected to the relay line, and the alternating current impedance is lowered between the base and emitter, so that the transistor has constant voltage receiving characteristics that are unaffected by signals such as audio that are alternating current components. This is what was given to him.

This is based on the fact that the power supply device on the exchange side that supplies DC loop current usually has a resistance of about 400Ω, and even if the receiving side is short-circuited, it will be protected by this 400Ω resistance.
A simple transistor circuit was constructed that has a constant voltage characteristic of several volts for direct current receiving voltage and high impedance characteristic for alternating current signals such as audio.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

A DC voltage is supplied from terminal 1 of the power receiving circuit to the base of transistor 19 via resistor 16 and Zener diode 17, and base current flows through transistor 19. This base current is minute, the voltage drop due to the resistor 16 is almost negligible, and the voltage between the collector and base of the transistor 19 (hereinafter referred to as Vcb) is equal to the Zener voltage of the Zener diode 17.

That is, when the collector currents of the transistors 19 and 20 are related to heat<Vcb, the voltage becomes a constant voltage.

Therefore, the residual voltage between terminals 1 and 2 of the power receiving circuit is also constant, exhibiting constant voltage power receiving characteristics.

The current flowing through transistors 19 and 20 returns to the DC power supply from terminal 2 through contact 3 for dial transmission, forming a loop current. Capacitor 18 bypasses signals such as audio, and together with resistor 16, the base voltage of transistor 19 In order to prevent this from changing, transistors 19 and 20 form a high impedance in terms of AC.

Here, for example, if the residual voltage is 4V, when the voltage of the DC power supply 11 shown in FIG. 3 is 48V, the resistance value of the relay 10 is 440Ω, and the resistance value of the relay line 14.15 is zero, the maximum loop current is , and the power consumption of the power receiving circuit is 0.4W.

FIG. 2 is a circuit diagram showing another embodiment of the present invention.

This uses a photocoupler 21 in place of the contact point 3 for dial transmission shown in FIG. When a dial pulse is applied between terminals 24 and 25, photocoupler 21 opens and closes the output of Zener diode 17.

When the photocoupler 21 cuts off the output of the Zener diode 17, the base voltage of the transistor 19 decreases due to the resistors 22 and 23, and the transistor 19 stops operating, so the transistor 20 also does not operate, and therefore the terminals 1 and 2
The loop current between the two ends is cut off.

When the photocoupler 21 connects the output of the Zener diode 17, the transistor 19 operates as in FIG. 1, forming a loop current between terminals 1 and 2 of the power receiving circuit.

〔Effect of the invention〕

As explained above, the present invention can significantly reduce the power consumption of the power receiving circuit compared to the conventional system, and has the effect of facilitating miniaturization of the device.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a circuit diagram showing another embodiment of the invention, and Fig. 3 is a diagram showing an example of a power receiving circuit using a conventional coil. . Figure':,tl'r E3.4 is the contact, l is the coil, 6 is the equivalent inductance, 7 is the equivalent resistance, 8 is the power receiving circuit, 9, 12.18
is a capacitor, 10 is a relay, 11 is a DC power supply, 13 is 2 cotton/
4-wire conversion circuit, 16, 22 and 23 are resistors, 17 is a Zener diode, 19 and 20 are transistors, and 21 is a photocoupler.

Claims (1)

[Claims] A DC loop type power receiving circuit that constitutes a pair of inter-office relay lines of an exchange includes a transistor connected between the inter-office relay lines, means for maintaining a DC voltage between the collector and base of the transistor at a constant value, and 1. A power receiving circuit for relaying between stations, comprising means for reducing AC impedance between a base and an emitter of a transistor.