JP2832762B2 - Public telephone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a public telephone provided with a power storage device for storing electric power by a small current flowing through a line during on-hook.

[0002]

2. Description of the Related Art Conventionally, as a public telephone, a control circuit for performing various operations (for example, storage of the number of coins stored in a safe of the public telephone, storage of a failure state of the public telephone, etc.) during on-hook has been provided. Things are in practical use.

[0003] Thus, power supply to the control circuit operating during the on-hook operation has been conventionally performed as shown in FIG.

That is, in FIG. 3, 1 is a public telephone, 2
Is the control circuit described above. Reference numeral 3 denotes a communication circuit of the public telephone 1, which is a line terminal L1, L
They are connected between the two via a hook switch h. The hook switch h opens in the on-hook state to disconnect the communication circuit 3 from the line terminals L1 and L2, and is closed in the off-hook state to connect the communication circuit 3 to the line terminals L1 and L2.

[0005] Between the line terminal L2 and the communication circuit 3,
The constant voltage diode ZD is connected. The connection between the line terminal L1 and the hook switch h and the connection between the constant voltage diode ZD and the communication circuit 2 are connected by a resistor R having a large resistance value. While the switch is in operation, line terminals L1, L
Due to the voltage applied between the two, when the line terminal L1 is +,

Line terminal L1 (+) → diode D1 →
A minute current flows through a loop of the resistor R → the constant voltage diode ZD → the diode D4 → the line terminal L2 (−).

D1 to D4 are diodes,
A rectifier circuit is configured to apply a voltage in the same direction to the constant voltage diode ZD even if the polarities of the line terminals L1 and L2 are inverted.

A power storage device 4 is connected to both ends of the constant voltage diode ZD, and is trickle-charged by a minute current loop at the time of on-hook.

[0009] The power stored in the power storage device 4 is:
It is supplied to the control circuit 2.

[0010]

However, in the conventional public telephone shown in FIG. 3, even after the required amount of power is stored in the power storage device 4, the loop between the exchange and the public telephone in the loop. Since a very small current is constantly flowing, a large power loss occurs when viewed from the exchange.

It is an object of the present invention to solve such a problem and to provide a public telephone which does not cause such power loss.

[0012]

In order to solve the above-mentioned problems, a public telephone according to the present invention detects a voltage of a power storage device, and outputs a disconnection signal when the voltage becomes higher than a first reference voltage. A monitoring circuit that outputs a connection signal when the voltage becomes equal to or lower than a second reference voltage lower than the first reference voltage, and disconnects the minute current loop by the disconnection signal from the monitoring circuit; And a switch circuit for connecting the loop.

[0013]

With this configuration, in the public telephone according to the present invention, when the voltage of the power storage device becomes equal to or higher than the first reference voltage, a disconnection signal is generated from the monitoring circuit, and the switch circuit is disconnected by this signal. For this reason, since the loop of the minute current in the on-hook state is cut, the minute current does not flow thereafter. Then, when the voltage of the power storage device drops and becomes equal to or lower than the second reference voltage, a connection signal is generated from the monitoring circuit. With this signal, the switch circuit is connected and a minute current loop is formed again. Electric power is stored.

[0014]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a public telephone 10 according to one embodiment of the present invention.

In FIG. 1, 2 is a control circuit, 3 is a speech circuit, L1 and L2 are line terminals, h is a hook switch that opens in an on-hook state and is closed in an off-hook state, R is a resistor, and ZD is a constant voltage. A diode, 4 is a power storage device,
D1 to D4 are diodes constituting a rectifier circuit,
Since these are the same as those of the conventional device shown in FIG. 3, their description will be omitted.

A switch circuit 11 is inserted between the resistor R and an intermediate point between the constant voltage diode ZD and the communication circuit 3.

When the voltage of the power storage device 4 is detected and becomes equal to or higher than a predetermined first reference voltage, a disconnection signal for turning off the switch circuit 11 is output, and a predetermined second reference voltage is turned off. When the voltage becomes equal to or lower than the voltage (a value lower than the first reference voltage), the monitoring circuit 12 that outputs a connection signal for turning on the switch circuit 11 is connected to the power storage device 4. The second reference voltage is set to a voltage at which the control circuit 2 can operate.

With this configuration, when the public telephone is not used, that is, in the on-hook state, the hook switch h is open and the communication circuit 3 is disconnected from the line terminals L1 and L2. Since the minute current loop is formed by the resistor R, power from the telephone line is stored in the power storage device 4 and supplied to the control circuit 2. When the voltage of the power storage device 4 becomes equal to or higher than a predetermined first reference voltage, the monitoring circuit 12 detects this and outputs a disconnection signal. As a result, the switch circuit 11 is turned off. For this reason,
The minute current loop of the resistor R is cut, and the minute current stops flowing.

When the voltage of the power storage device 4 falls below the second reference voltage due to the operation of the control circuit 2 or the natural discharge of the power storage device 4, the monitoring circuit 1
2 detects this and outputs a connection signal. As a result, the switch circuit 11 is turned on, a minute current flows again, and power is stored in the power storage device 4. And the first
Is cut off again when the reference voltage becomes equal to or higher than the reference voltage.

FIG. 2 shows a more specific circuit configuration of one embodiment of the present invention.

That is, in FIG. 2, the power storage device 4 is constituted by a capacitor C, for example. Switch circuit 11
Is composed of, for example, a photocoupler PC. The monitoring circuit 12 includes, for example, a voltage detector 12a and a resistor 12b.

When the voltage of the capacitor C becomes higher than the first reference voltage, the output of the voltage detector 12a becomes "H". For this reason, the photocoupler PC is turned off, and the loop of the minute current is cut. When the voltage of the capacitor C falls below the second reference voltage due to the power consumption of the control device 2 or the spontaneous discharge of the capacitor C, the voltage detector 12a
Becomes "L", the photocoupler PC is turned on, and the charging of the capacitor C is started again.

Although the embodiment of the present invention has been described above, it goes without saying that various modifications can be made in the configuration of each part.

[0025]

As described above, the public telephone of the present invention outputs a disconnection signal when the voltage of the power storage device exceeds the first reference voltage and outputs a connection signal when the voltage of the power storage device falls below the second reference voltage. Since a monitoring circuit and a switch circuit for disconnecting the microcurrent loop by the disconnection signal from the monitoring circuit and connecting the microcurrent loop by the connection signal are provided, when the power storage device 4 reaches a constant voltage, It is possible to prevent a minute current from flowing through the line unnecessarily, and to eliminate a large power loss as seen from the switching center side in the conventional public telephone shown in FIG.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing a specific circuit configuration of one embodiment of the present invention.

FIG. 3 is a circuit diagram showing a conventional public telephone.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Public telephone 2 Control circuit 3 Communication circuit 4 Power storage device 10 Public telephone 11 Switch circuit 12 Monitoring circuit 12a Voltage detector 12b Resistor L1, L2 Line terminal h Hook switch ZD Constant voltage diode R Resistor D1-D4 Diode C Capacitor PC Photocoupler

Claims (1)

(57) [Claims] 1. A public telephone that stores power from a line in a power storage device via a minute current loop during on-hook, detects a voltage of the power storage device, and detects the voltage to be higher than a first reference voltage. Then, a disconnection signal is output and the first
And a monitoring circuit that outputs a connection signal when the voltage becomes equal to or lower than a second reference voltage lower than the reference voltage of the reference voltage. The microcurrent loop is disconnected by the disconnection signal from the monitoring circuit, and the microcurrent loop is connected by the connection signal. A public telephone comprising a switch circuit.