JPH0846728A - Feeding control switch circuit for line terminator - Google Patents

Abstract

PURPOSE:To suppress the increase of power consumption of the circuit and cost increase when power is supplied to the network terminator. CONSTITUTION:A switch 11 controlling signal transmission between a network terminator 14 and an exchange 15 is arranged between one terminal of transmission reception circuits 2, 3 and a 2-wire metallic line 13 and switches 7, 8 used to supply positive or negative power from the feeding circuit to the network terminator are arranged between a connecting point between the switch 11 and the line 13 and a feeding circuit 1. As a result, no signal is sent to the switches 7, 8 and then an inexpensive switch is in use and when a current of a prescribed value or more less is detected by a current detection circuit 9 in the case of communication, the power to the network terminator is stopped to suppress the power consumption of the circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply control switch circuit for a line terminating device, and more particularly to a power supply control switch circuit for dual wire bidirectional communication power supply.

[0002]

2. Description of the Related Art FIG. 2 shows a line termination unit (OCU) of this type.
It is a block diagram of. In the figure, 101 is a power feeding circuit, 102 is a signal receiving circuit, 103 is a signal transmitting circuit, 1
Reference numeral 04 is an AC cutoff filter, and 105 is a DC cutoff circuit. Further, 106 is a transmission / reception transformer, 107 is a positive power feeding switch, 108 is a reverse polarity power feeding switch, and 109 is a current detection circuit.

A network terminating device (DSU) is connected to a terminal 110 provided in the line terminating device via a subscriber line. In the line terminating device, when the network terminating device is not in communication, the positive polarity power feeding switch 107 is turned on and the reverse polarity power feeding switch 108 is turned off,
As a result, positive power is supplied from the power supply circuit 101 to the network terminating device. In this case, since the communication is not being performed, the signal receiving circuit 102 and the signal transmitting circuit 103 have stopped their operations, and the current detection circuit 109 outputs a low current as the detection result. This is because the network terminating device has low power consumption during non-communication.

On the other hand, at the time of communication of the network terminating device, in the line terminating device, the positive polarity power supply switch 107 is turned off and the reverse polarity power supply switch 108 is turned on, so that the power supply circuit 101 supplies power of reverse polarity. To be done. At this time, communication is performed via the signal receiving circuit 102 and the signal transmitting circuit 103.

[0005]

In such a conventional line terminating device, the network terminating device must always supply power regardless of whether the network terminating device requires power supply during communication. Therefore, there is a drawback that the power consumption increases. Moreover, since the positive polarity power supply switch 107 and the reverse polarity power supply switch 108 are arranged on the path of the signal to be transmitted and received, it is necessary to use an expensive semiconductor switch having excellent linearity. Therefore, there is also a drawback that the cost of the circuit increases.

Therefore, an object of the present invention is to suppress an increase in power consumption of a circuit and an increase in cost when supplying power to a network terminating device.

[0007]

In order to solve such a problem, the present invention supplies power to a network terminating device connected to a two-wire metallic line and connected to the two-line metallic line. A power supply circuit and a transmission / reception circuit, one end of which is connected to the two-wire metallic line and the other end of which is connected to an exchange, and which transmits a signal for digital communication between the fed network terminating device and the exchange via the metallic line. In a line terminating device including and,
A first switch disposed between the wire metallic line and the network terminating device and the switch to control signal transmission; and a connection point between the first switch and the two-wire metallic line and a power supply circuit. And a second switch for supplying power of either positive polarity or reverse polarity from the power feeding circuit to the network terminating device. Further, the detecting means for detecting the power supply current during the communication between the fed network terminating device and the exchange, and when the detection output of the detecting means is below a certain value, the second switch is turned off to send the signal to the network terminating device. And means for stopping power supply.

[0008]

A first switch for controlling signal transmission between the network terminating device and the exchange is provided between one end of the transmission / reception circuit and the two-wire metallic line, and the first switch and the two-wire metallic line are connected. A second switch is provided between the connection point with the line and the power supply circuit for supplying power from the power supply circuit to the network terminating device with either positive polarity or reverse polarity. As a result, since a signal is not transmitted through the second switch, an inexpensive switch can be used as the second switch, and thus an increase in circuit cost can be prevented. Further, the fed network termination device and the exchange detect the feeding current during communication, and when the value of the detected current is below a certain value, the feeding to the network termination device is stopped. As a result, the power consumption of the circuit can be suppressed as compared with the conventional circuit that constantly supplies power to the network terminating device.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a power supply control switch circuit of a line terminating device according to the present invention. In the figure, this embodiment circuit includes a power feeding circuit 1, a signal receiving circuit 2, a signal transmitting circuit 3, and an AC cutoff filter 4.
, A DC cutoff circuit 5, a transmission / reception transformer 6, a positive polarity power feeding switch 7, a reverse polarity power feeding switch 8 and a current detection circuit 9, and a terminal 1 via a two-wire metallic line.
It also supplies power to the network terminating device 14 connected to 0. The line indicated by reference numeral 13 is also formed by a two-line metallic line.

Here, the difference from the conventional circuit shown in FIG.
A DC blocking circuit 5 and a transmission / reception transformer 6 are provided between the terminal 10 and the positive polarity power supply switch 7 and the reverse polarity power supply switch 8, and the signal transmission / reception circuits 2 and 3 are connected to the transmission / reception transformer 6. A switch 11 is provided between the DC cutoff circuit 5 and the terminal 10.

By the way, in the circuit of this embodiment, when waiting for an outgoing call during non-communication, the positive polarity power supply switch 7 is turned on and the reverse polarity power supply switch 8 is turned off to supply power to the network terminating device. A positive power source is supplied from the circuit 1. Here, when the exchange 15 transmits to the network terminating device via the signal receiving circuit 2, the communication line is short-circuited in the network terminating device 14. Therefore, the current of this communication line is terminal 1
0, the positive polarity power supply switch 7 and the AC cutoff filter 4, and the current detection circuit 9 detects the result. Based on the detection result, it can be detected by the circuit of this embodiment that the exchange has transmitted.

In this case, in the circuit of this embodiment, in order to activate the network terminating device 14, the positive power feeding switch 7 is turned off,
The reverse polarity power supply switch 8 is turned on to supply the power of the reverse polarity from the power supply circuit 1 to the network terminating device 14 to notify the start of communication. However, at this time, if a low current is detected by the current detection circuit 9, it means that the network terminating device 14 itself has a local power feeding function, so that the control circuit 16 turns on the switch control output to set the positive polarity. Both the power feeding switch 7 and the reverse polarity power feeding switch 8 are turned off, and the network terminating device 1
The power supply to 4 is stopped.

Even if both the positive polarity power feeding switch 7 and the reverse polarity power feeding switch 8 are turned off, the signal passing through the signal receiving circuit 2 and the signal transmitting circuit 3 passes through only the switch 11 and the switches 7, 8 Since it does not go through, it becomes possible to continue communication. Further, when it is necessary to disconnect each circuit of the line terminating device when testing a communication line (subscriber line), each switch 7, 8 and switch 1
By turning 1 off, complete separation can be performed. In this case, the switch 12 is turned on, and the subscriber line is tested through the switch 12.

As described above, by providing the switch 11 for disconnecting the transmission / reception circuits 2 and 3 in addition to the switches 7 and 8 which are the power supply control circuits, the network terminating device 14 can be used during communication.
On the other hand, when power supply is unnecessary, it is possible to suppress power consumption by turning off the switches 7 and 8 while keeping the switch 11 on. Also, since transmitted / received signals are not transmitted through the switches 7 and 8, inexpensive switches can be used in place of the expensive 4 semiconductor switches having excellent linearity, and therefore the circuit is composed of these inexpensive 4 switches. Since it can be configured with the above switch and one switch 11 for transmitting the above-mentioned AC signal, the cost can be reduced.

[0015]

As described above, according to the present invention, 2
A power supply circuit that is connected to the wire metallic line and that supplies power to the network terminating device that is connected to the two-wire metallic line; one end is connected to the two-wire metallic line and an exchange is connected to the other end; In a line terminating device having a transmitter / receiver circuit for transmitting a signal for digital communication between a fed network terminating device and a switch, a network is provided between one end of the transmitter / receiver circuit and a two-wire metallic line. A first switch for controlling signal transmission between the terminating device and the exchange is provided, and between the connection point between the first switch and the two-wire metallic line and the power supply circuit, the power supply circuit to the network termination is provided. Since the second switch for supplying the power source of either the positive polarity or the opposite polarity to the device is provided, the second switch is provided because a signal is not transmitted through the second switch. It can be used an inexpensive switch as switch, thus preventing the cost of the circuit. In addition, since the fed current is detected during communication between the network terminating equipment and the exchange, and if the detected current value is less than a certain value, the power feeding to the network terminating equipment is stopped. The power consumption of the circuit can be suppressed as compared with the conventional circuit that supplies power to the network terminating device.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a conventional circuit.

[Explanation of symbols]

1 ... Power feeding circuit, 2 ... Signal receiving circuit, 3 ... Signal transmitting circuit,
4 ... AC cutoff filter, 5 ... DC cutoff circuit, 6 ... Transmission / reception transformer, 7 ... Positive polarity power supply switch, 8 ... Reverse polarity power supply switch, 9 ... Current detection circuit, 11 ... Communication switch, 12 ... Test switch , 13 ... metallic track, 1
4 ... Network terminating device, 15 ... Switch, 16 ... Control circuit.

Claims (2)

[Claims] 1. A power supply circuit connected to a two-wire metallic line and supplying power to a network terminating device connected to the two-wire metallic line, and one end connected to the metallic line and the other end A line terminating device connected to an exchange, comprising a power supply and a network terminating device and a transmitter / receiver circuit for transmitting a signal digitally communicated between the exchange and the metallic line, wherein one end of the transmitter / receiver circuit is provided. A first switch disposed between the two-wire metallic line and controlling the signal transmission between the network terminating device and the exchange; a connection point between the first switch and the two-line metallic line; A second power supply circuit arranged between the power supply circuit and the power supply circuit for supplying power of either positive polarity or reverse polarity to the network terminating device;
A power supply control switch circuit for a line terminating device, comprising: 2. The power supply control switch circuit of the line terminating device according to claim 1, wherein the detecting means for detecting a power supply current during communication between the fed network terminating equipment and the exchange, and the detection output of the detecting means. And a means for stopping power supply to the network terminating device by turning off the second switch when the value is equal to or less than a certain value.