JPS61294957A - Telephone set circuit - Google Patents

Abstract

PURPOSE:To reduce the power consumption of a terminal equipment and to expand the transmission range by providing a power failure detection circuit, a transmission/reception circuit supplying a power failure code signal and a DC power supply, a self-holding relay and a control circuit. CONSTITUTION:When a commercial power supply 12 is failed, it is detected by a power failure detection circuit 18 of a master set, a contact of the self- holding relay 20 is connected to an external line telephone line 11 by using a drive pulse signal from a control circuit 19 to connect the line 11 and an extension line 16. Further, a changeover contact of the self-holding relay 28 is connected to a privacy call circuit 23. Then a privacy call circuit 23 of a terminal telephone set 13 is connected to the line 11 via a hook switch 27 and the terminal telephone set 13 receives the supply of DC power from the line 11 to become a talking state. Thus, it is not required to flow normally to an exciting current to a coil 34 against power failure.

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 of 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 a 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 disconnected by the force of the relay's return spring. It is now connected. 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,
When multiple terminal telephones are connected in parallel to the transmission path to the main device that performs exchange processing, and DC power is supplied to each terminal telephone from the main device connected to the commercial power supply, a relatively large current for driving the relay is transmitted. We have to keep it flowing into the streets. For this reason, transmission loss increases, making it impossible to extend the transmission distance, and a relatively large guest room 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. As shown in FIG. 1, the main device 10 that performs the exchange process is connected to an outside telephone line 11 and an AC commercial power source 12, and a plurality of terminal telephones 13 are connected to one car [10] in a two-wire system. They are connected in parallel by an extension telephone line 16 consisting of a speech line 14 and a two-wire control line 15.

The main device 10 receives a voltage of, for example, 24V from an AC commercial power source 12.
A power supply circuit 17 for obtaining a DC power supply V of volts, a power failure detection circuit 18 for detecting a voltage drop in this power supply circuit 17 and sending out a power failure detection signal, and connecting a communication line 14 to an external telephone line 1.
A self-holding relay 20 has a switching contact that connects to 1 and a DC power source 1, and a drive pulse signal is supplied to the self-holding relay 20 to set the switching contact to the external telephone line 11 upon receiving a power failure detection signal. At the same time, a control circuit 1 generates a power outage code signal corresponding to the power outage detection signal.
9, and a transmitting/receiving circuit 21 that sends the power outage code signal and the power supply voltage from the DC power supply (2) to the control line 15. Note that the ringer circuit 41 that receives the calling signal is
It is connected to an outside telephone line 11.

The terminal telephone a13 is connected to a confidential communication circuit 23, a handset 24, a loudspeaker circuit 25 for performing loudspeaking calls or loudspeaker reception, a loudspeaker 26, a hook switch 27, and a control line 15, and transmits signals from the main device 10. A transmitting/receiving circuit 22 receives the received power outage code signal and DC power source ■, a switching contact for switching and connecting the extension telephone line 16 to the confidential communication circuit 23 and the loudspeaker circuit 25, and an opening/closing contact connected in parallel to the hook switch 27. a self-holding relay 28 and a transmitting/receiving circuit 22
A control circuit 29 is provided which receives a power outage code signal from the self-holding relay 28, sets a switching contact in the confidential communication circuit 23, and supplies a drive pulse signal to set the open/close contact to the "open" state.

Various types of self-holding relays 20 and 28 have been put into practical use, and FIG. 2 shows a principle diagram of one example.

U-shaped yokes 31 are arranged facing each other in contact with the S and N poles of the permanent magnet 3o, and the iron core 33 is rotatably supported at the center so that both ends move in the magnetic gap 32. An excitation coil 34 is wound around. coil 34
When a driving pulse signal is applied to the coil 34, the iron core 33 is magnetized depending on the polarity of the pulse signal and rotates clockwise or counterclockwise, forming a temporally closed circuit shown by dotted lines and arrows, and the pulse signal is no longer supplied to the coil 34. However, the state is maintained by the action of the permanent magnet 30. The movable contacts of the self-holding relays 20 and 28 are connected to the iron core 13.
It is configured to work with.

As shown in FIG. 3, the power failure detection circuit 18 of the main device 10 includes a voltage dividing resistor 35 that divides the voltage of the N source circuit 17, a reference voltage 36, and a comparator 37. When the voltage drops from the normal 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 expressed as '
Although the power supply transformer 38 is monitored, a drop in the AC voltage on the secondary side of the power transformer 38 may be monitored to detect a power outage state.

(Function) With this configuration, when the commercial power supply 12 has a power outage, it is detected by the power outage detection circuit 18 of the main device, and the control circuit 1
Self-holding relay 2 is activated by the drive pulse signal from 9.
The contact o is connected to the outside telephone line 11, and the outside telephone line 11 and the extension 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 switching contact of the self-holding relay 28 is connected to the confidential communication circuit 23 by the drive pulse signal from the control circuit 19. , the switching contacts are opened. Then, the confidential communication circuit 23 of the terminal telephone 13 is connected to the external telephone line 11 via the hook switch 27, and even if the commercial power supply 12 is interrupted, the terminal telephone 13 can be connected to the external telephone line 11 by direct current. After receiving the R source, it becomes ready to talk like a normal telephone. The electric power required from the time a power failure 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.
6, the transmission loss is reduced, and the possible transmission distance between the main device 10 and the terminal telephone 13 is extended. Furthermore, by reducing power consumption for driving the relays 20 and 28, the power supply circuit 17 of the main device 10 is simplified and miniaturized.

(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. Various excellent effects can be obtained, such as being able to extend the transmission distance between telephones and setting terminal telephones to a state where they can make calls during a power outage.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a telephone circuit implementing this 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 main parts of the main device. 10... Main device, 11... External telephone line, 12...
・Commercial MS, i3-・Terminal telephone, 16・Internal a telephone line, 17・Power supply circuit, 18・Power failure detection circuit, 19・2・・Control circuit, 20・28・・・Self-holding relay, 23... Confidential communication circuit, 25... Loudspeaker circuit, 40... Smoothing capacitor. Figure 1

Claims (1)

[Claims] A main device that is connected to an external telephone line and receives power from an AC commercial power supply and a terminal telephone that can also be used for private voice amplification are connected by an extension telephone line, and the main device has a power supply circuit that obtains DC power from the AC power supply, and a power outage detection circuit that detects a power outage in the AC commercial power supply due to a voltage drop in the power supply circuit and generates a power outage detection signal; and a power outage detection circuit for supplying the DC power and a power outage code signal corresponding to the power outage detection signal to the terminal telephone. a self-holding relay having a transmitting/receiving circuit, the terminal telephone 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 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.