JPH0462505B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention is applicable to telephones that are connected to an external telephone line and receive power for operating various additional functions from a commercial power supply when the commercial power supply fails. However, it is related to the telephone circuitry necessary to maintain the minimum call function as a telephone.

(Prior Art) Conventionally, there has been a telephone circuit of this type in which a loudspeaker circuit and a secret telephone circuit are connected to the telephone line by switching between them. The amplifiers and relays in the loudspeaker circuit are supplied with DC power obtained from the commercial power supply, and when a power outage occurs, power is no longer supplied to the relay, and the telephone line and confidential communication circuit are connected to each other by the force of the relay's return spring. It is now connected with Power was always supplied to the relay during loudspeaker calls during normal times, not during power outages.

(Problem to be Solved by the Invention) In this way, for example, in a button telephone device, a plurality of terminal telephones are connected in parallel to the transmission path to the main device that performs switching processing, and the main device is connected to a commercial power source. When supplying direct current power to each terminal telephone from the terminal, a relatively large current for driving the relay must continue to flow through the transmission line. As a result, transmission loss increases, making it impossible to extend the transmission distance, and a relatively large capacity is required as a power supply circuit for the main device, making it difficult to reduce the size and weight.

(Means for Solving the Problems) The present invention solves the above-mentioned conventional problems, reduces the power consumption of terminal devices such as telephones, reduces the size and weight of the power supply circuit of the main device, and reduces the transmission distance. The purpose is to provide a telephone circuit that can extend the

The present invention will be described in detail below based on embodiments shown in the drawings. The main device 10 that performs the exchange process is
As shown in FIG. 1, a plurality of terminal telephones 13 are connected to an external telephone line 11 and an AC commercial power supply 12, and a two-wire communication line 14 is connected to one main unit 10.
and an extension telephone line 16 consisting of a two-wire control line 15
are connected in parallel by.

The main device 10 includes a power supply circuit 17 for obtaining a DC power supply V having a voltage of, for example, 24 volts from an AC commercial power supply 12, and a power failure detection circuit 18 for detecting a voltage drop in the power supply circuit 17 and transmitting a power failure detection signal. A self-holding relay 20 has a switching contact that switches and connects the communication line 14 to the outside telephone line 11 and the DC power supply V, and a self-holding relay 20 that receives a power failure detection signal and sets the switching contact to the outside telephone line 11. A control circuit 19 that supplies a drive pulse signal for the power outage and also generates a power outage code signal corresponding to a power outage detection signal, and a transmitting/receiving circuit 21 that sends out this power outage code signal and the power supply voltage from the DC power supply V to the control line 15. Prepared. Note that the ringer circuit 41 that receives the calling signal is connected to the outside telephone line 11.
It is connected to the.

The terminal telephone 13 includes a private conversation circuit 23, a handset 24, a loudspeaker circuit 25 for performing loudspeaker calls or loudspeaker reception, a loudspeaker 26, and a switch 27.
, a transmitting/receiving circuit 22 connected to the control line 15 and receiving the power outage code signal and DC power supply V sent from the main device 10, and a confidential communication circuit 2 connecting the extension telephone line 16.
3 and amplification circuit 25, and a self-holding relay 28 having an opening/closing contact connected in parallel with the hook switch 27; and a control circuit 29 for supplying a drive pulse signal for setting the secret line in the confidential communication circuit 23 and setting the opening/closing contact to the "open" state.

Various types of self-holding relays 20 and 28 have been put into practical use, and the principle of one example is shown in FIG. 2. U-shaped yokes 31 are placed facing each other in contact with the S and N poles of the permanent magnet 30, and the iron core 33 is placed so that both ends move through the magnetic air 32.
is rotatably supported at the center, and an excitation coil 34 is wound around the iron core 33. When a driving pulse signal is applied to the coil 34, the iron core 33 is magnetized depending on the polarity of this pulse signal and rotates clockwise or counterclockwise.
A temporally closed circuit shown by dotted lines and arrows is formed,
Even if the pulse signal is no longer supplied to the coil 34, the state is maintained by the action of the permanent magnet 30. The movable contacts of the self-holding relays 20 and 28 are configured to interlock with the iron core 13.

As shown in FIG. 3, the power failure detection circuit 18 of the main device 10 includes a voltage dividing resistor 35 for dividing the voltage of the power supply circuit 17, a reference voltage 36, and a comparator 37. When the voltage drops from 24 volts to 18 volts, a power failure detection signal is output from the comparator 37. Here, the voltage of the DC power supply V after passing through the rectifier 39 and smoothing capacitor 40 on the secondary side of the power transformer 38 is monitored, but the drop in AC voltage on the secondary side of the power transformer 38 is monitored. However, a power outage state may be detected.

(Function) With this configuration, when a power outage occurs in the commercial power supply 12, it is detected by the power outage detection circuit 18 of the main device, and the contacts of the self-holding relay 20 are activated by the drive pulse signal from the control circuit 19. It is connected to the external telephone line 11, and the external telephone line 11 and the internal telephone line 16 are connected to each other. At the same time, a power outage code signal is sent from the transmitting/receiving circuit 21 to the terminal telephone 13 via the communication line 14, and the control circuit 19
The switching contact of the self-holding relay 28 is connected to the confidential communication circuit 23 by the drive pulse signal from the
The switching contacts are opened. And outside telephone line 1
1, the confidential communication circuit 23 of the terminal telephone 13 is connected via the switch 27, and even if the commercial power supply 12 is out of power, the terminal telephone 13 receives DC power from the external telephone line 11 and operates normally. You can now make calls in the same way as with other telephones. The power required from the time a power outage occurs until the self-holding relays 20 and 28 operate is covered by the electric charge stored in the smoothing capacitor 40 of the power supply circuit. In this way, by using the self-holding relays 20 and 28, there is no need to keep the excitation current flowing through the coil 34 during normal times in case of a power outage, so the current flowing through the extension telephone line 16 is reduced. Transmission loss is reduced, and the possible transmission distance between main device 10 and terminal telephone 13 is extended. moreover,
By reducing the power consumption for driving the relays 20 and 28, the power supply circuit 17 of the main device 10 can be simplified and downsized.

(Effects of the Invention) As described above, according to the present invention, the power supplied from the main device to the terminal telephone can be reduced, the power supply circuit of the main device can be downsized, and the power supply circuit between the main device and the terminal can be reduced. The transmission distance between telephones can be extended, and terminal telephones can be set to be ready for calls in the event of a power outage.
Various excellent effects can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a telephone circuit embodying the present invention, FIG. 2 is a principle explanatory diagram showing an example of a self-holding relay, and FIG. 3 is a circuit block diagram of the essential parts of the main device. 10... Main device, 11... External telephone line, 12... Commercial power supply, 13... Terminal telephone, 16... Extension telephone line, 17... Power supply circuit, 18... Power outage detection circuit, 1
9, 29... Control circuit, 20, 28... Self-holding relay, 23... Confidential communication circuit, 25... Loudspeaker circuit, 4
0...Smoothing capacitor.

Claims (1)

[Claims] 1. A main device connected to an external telephone line and supplied with power from an AC commercial power source and a terminal telephone that can also be used for confidential voice amplification are connected by an extension telephone line, and the main device has a power supply circuit that receives DC power from the AC power source. a power outage detection circuit that detects a power outage in the AC commercial power source due to a voltage drop in the power supply circuit and generates a power outage detection signal; and supplies a power outage code signal corresponding to the power outage detection signal and the DC power source to the terminal telephone. The terminal telephone is a self-holding type having a circuit for confidential communication, a circuit for amplification, and a switching contact for switching and connecting the extension telephone line to the circuit for amplification and the circuit for confidential communication. A telephone circuit comprising: a relay; and a control circuit that supplies a drive pulse signal to the self-holding relay for connecting the switching contact to the loudspeaker circuit when the power outage code signal is received.