JPH04104546A - Polarity inversion detection - Google Patents

Abstract

PURPOSE:To detect the polarity of a DC current supplied through a telephone line without increasing the DC voltage drop of a telephone terminal equipment by detecting inversion of the polarity of a DC power source by the output signal of a photocoupler. CONSTITUTION:In a diode bridge 109, the diode where a DC current (i) flows is changed by inversion of the polarity of a DC power source 100. Consequently, a part of diodes constituting the diode bridge 109 is substituted with the diode part of a photocoupler 106 to detect inversion of the polarity of the DC current (i) by an output signal (d) of the photocoupler 106. The characteristic of the diode part of the photocoupler 106 is equalized to that of diodes constituting the diode bridge 109 to prevent the voltage drop in a telephone terminal equipment 1 from being increased by insertion of the photocoupler 106. Thus, the telephone terminal equipment can detect inversion of the polarity of the DC current without a bad influence upon the DC current supply source.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a polarity reversal detection method in a telephone terminal device that is supplied with a direct current whose polarity is reversed via a telephone line, without increasing the direct current voltage drop of the telephone terminal device as much as possible. The purpose is to make it possible to detect the polarity of the DC current supplied via the telephone line, and the DC current supplied via the telephone line is rectified by a diode bridge from a DC power supply whose polarity is reversed. In a telephone terminal device that supplies internal circuits, a part of the diode constituting the diode bridge is composed of a photocoupler diode part,
It is configured to detect polarity reversal of the DC power supply using the output signal of the photocoupler.

[Industrial application field]

The present invention relates to a polarity reversal detection method in a telephone terminal device that is supplied with a direct current whose polarity is reversed via a telephone line.

[Conventional technology]

FIG. 3 is a diagram showing an example of a conventional telephone terminal device.

In FIG. 3, a telephone terminal device 1 is connected via a telephone line 2 to an exchange (not shown).

The telephone terminal device 1 includes a capacitor 101, a tone ringer circuit 102, a sounder (S) 103, and a hook switch 10.
4. Polarity reversal detection circuit 105, diode bridge 10
9, dial circuit 110, cross point switch circuit 111, number buttons 112, telephone call circuit 113, transmitter (
114, a receiver (R) 115, a processor 116, and a terminal device 117.

The exchange supplies direct current i to telephone terminal device 1 in an off-hook state via telephone line 2, but the polarity of direct current i is reversed depending on the connection state.

For example, when making a call from the telephone terminal device 1, first set the telephone line L1 of the telephone line 2 to the (+) polarity, and set the telephone line L2 to the (-) polarity.
However, when the receiving telephone terminal device (not shown) responds, the direct current i supplied to the telephone terminal device 1 is switched to the (+) polarity of the telephone line L2 and the telephone line Ll The polarity is reversed to DC current i with (-) polarity.

Note that even if the polarity of the DC current i flowing from the telephone line 2 is reversed, the DC current i' flowing to the dial circuit 110, crosspoint switch circuit 111, and speech circuit 113 is rectified by the diode bridge 109, so remains constant.

Further, in addition to performing voice calls using the transmitter (T) 114 and receiver (R) 115, the telephone terminal device 1 can also perform communications other than voice using the processor 116 and the terminal device 117.

The telephone number input from the terminal device 117 is sent to the processor 1.
16 transmits the message to the dialing circuit 110 via the crosspoint switch circuit 111, so that when a call is made to an exchange (not shown) using the automatic dialing method, the response of the terminal device (not shown) on the receiving side is transmitted to the dialing circuit 110 via the crosspoint switch circuit 111. The need arises for detection.

For this purpose, a polarity reversal detection circuit 105 is provided.

The polarity reversal detection circuit 105 includes a diode bridge 109
A photocoupler 106 inserted in series into the inflow path of the DC current i before rectification by the converter detects polarity reversal of the DC current i supplied from the exchange.

That is, before the receiving terminal device responds, the telephone line L1 of the telephone line 2 is connected from the exchange to the telephone terminal device ll (+
) polarity, and since the telephone line L2 is supplied with a DC current i that has (-) polarity, the DC current i flows through the diode section of the photocoupler 106 and sets the transistor section of the photocoupler 106 in a conductive state. , sets the polarity inversion detection signal d transmitted to the processor 116 to L level.

When the terminal device on the called side responds, the telephone line L2 of the telephone line 2 is connected from the exchange to the telephone terminal device 1.

Direct current i with (+) polarity and telephone line L1 with (=) polarity
Since the direct current i is supplied to the diode 107
Since the photocoupler 106 does not pass through the diode section, the transistor section of the photocoupler 1.6 is set to a cutoff state, and the polarity reversal detection signal d transmitted to the processor 116 is set to H level.

The processor 116 detects a response from the terminal device on the receiving side by changing the polarity reversal detection signal d from the L level to the H level, and notifies the terminal device 117 of the response.

[Problem to be solved by the invention]

As is clear from the above explanation, in a conventional telephone terminal device, the photocoupler 106 and the diode 107 constituting the polarity reversal detection circuit 105 were inserted in series in the inflow path of the direct current i in the telephone terminal device 1. Therefore, the DC voltage drop within the telephone terminal device 1 increases by the voltage drop of the photocoupler 1o6 (or diode 107) (for example, about 2 volts DC), that is, the DC resistance within the telephone terminal device 1 increases, and the There was a possibility that the operation would be adversely affected.

An object of the present invention is to make it possible to detect the polarity of a direct current supplied via a telephone line without increasing the direct current voltage drop of a telephone terminal device as much as possible.

[Means to solve the problem] FIG. 1 is a diagram showing the principle of the present invention.

In FIG. 1, 1 is a telephone terminal device to which the present invention is applied, 200 is an internal circuit of the telephone terminal device 1, 109 is a diode bridge, 2 is a telephone line, 100 is a DC power supply whose polarity is reversed, and i is a DC power supply. 100 is a direct current supplied to the telephone terminal device l via the telephone line 2.

106 is a photocoupler provided in the diode bridge 109 according to the present invention.

The diode portion of the photocoupler 106 constitutes one of the diodes constituting the diode bridge 109.

[Effect]

When the polarity of the DC power supply 100 is reversed, the diode bridge 109 changes to become a diode through which the DC current i flows.

Therefore, by replacing part of the diodes constituting the diode bridge 109 with the diode section of the photocoupler 106, it becomes possible to detect the polarity reversal of the DC current i from the output signal d of the photocoupler 106.

Furthermore, by making the characteristics of the diode portion of the photocoupler 106 the same as those of the diodes constituting the diode bridge 109, the voltage drop within the telephone terminal device 1 is prevented from increasing due to the insertion of the photocoupler 106.

Therefore, the telephone terminal device can detect polarity reversal of the DC current without adversely affecting the DC current supply source.

〔Example〕

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

FIG. 2 is a diagram showing a telephone terminal device according to an embodiment of the present invention. Note that the same reference numerals indicate the same objects throughout the figures.

In FIG. 2, the DC power supply 100 in FIG. 1 is omitted as in FIG. 3, and the internal circuit 200 in FIG. 11
3, a transmitter (T) 114, a receiver (R) 115, a processor 116, and a terminal device 117 are shown.

In addition, in FIG. 2, the photocoupler 106 and the resistor 1
08 constitutes the polarity reversal detection circuit 105, and the diode part of the photocoupler 106 or the diode 1091.1
Diode bridge 109 with 093 and 1094
It consists of

In FIG. 2, the processor 116 inputs the telephone number input from the terminal device 117 to the crosspoint switch circuit 1.
11 to the dialing circuit 110, when a call is made to an exchange (not shown) using the automatic dialing method, before the receiving terminal (not shown) responds, from the exchange to the telephone terminal 1, Telephone line L of telephone line 2
A direct current l is supplied with the telephone line L2 having the (+) polarity and the telephone line L2 having the (-) polarity.

In such a case, the direct current i is the telephone line L of the telephone line 2.
From 1, hook switch 104, diode bridge 1
09, a dial circuit 110 and a telephone call circuit 113 connected in parallel, and a photocoupler 1
Telephone line L of telephone line 2 via the diode section of 06
It flows to 2.

As a result, the transistor portion of the photocoupler 106 is set to a conductive state, and the polarity reversal detection signal d transmitted from the polarity reversal detection circuit 105 to the processor 116 is set to the L level.

When the terminal device on the receiving side responds, the exchange supplies the telephone terminal device l with a direct current i such that the telephone line L2 of the telephone line 2 has the (+) polarity and the telephone line L1 has the (-) polarity.

In such a case, the direct current i is the telephone line L of the telephone line 2.
2 flows to the telephone line L1 of the telephone line 2 via the diode 1093 that constitutes the diode bridge 109, the dial circuit 110 and the telephone call circuit 113 connected in parallel, the diode 1094 that constitutes the diode bridge 109, and the hook switch 104. .

As a result, the transistor section of the photocoupler 106 is set to a cut-off state, and the polarity reversal detection signal d transmitted from the polarity reversal detection circuit 105 to the processor 116 is set to H level.

The processor 116 detects a response from the terminal device on the receiving side by changing the polarity reversal detection signal d from the L level to the H level, and notifies the terminal device 117 of the response.

As is clear from the above description, according to the present embodiment, by configuring the diodes 1091, 1093 and 1094, and the diode portion of the photocoupler 106 that constitutes the polarity reversal detection circuit 105, a telephone call can be made via the telephone line 2. It becomes possible to detect polarity reversal of the DC current i supplied to the terminal device 1.

Further, by making the characteristics of the diode portion of the photocoupler 106 the same as those of the diode 1091, etc., the voltage drop in the telephone terminal device 1 will not increase due to the provision of the polarity reversal detection circuit 105.

Note that FIG. 2 is only one embodiment of the present invention, and for example, the diode portion of the photocoupler 106 is not limited to being inserted into the illustrated position of the diode bridge 109, and may be inserted into other diodes 1091. , 1093 or 1094 may be considered, and in any case, the effect of the present invention remains the same. It goes without saying that the telephone terminal device 1 to which the present invention is applied is not limited to that shown in the drawings.

〔Effect of the invention〕

As described above, according to the present invention, in the telephone terminal device, it is possible to detect polarity reversal of DC current without adversely affecting the DC current supply source.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram showing a telephone terminal device according to an embodiment of the present invention, and FIG. 3 is a diagram showing an example of a conventional telephone terminal device. In the figure, ■ is a telephone terminal device, 2 is a telephone line, and 100
101 is a DC power supply, 101 is a capacitor, 102 is a tone ringer circuit, 103 is a sounder (S), 104 is a hook switch, 105 is a polarity reversal detection circuit, 106 is a photocoupler, 107.1091 to 1094 are diodes, 108
is a resistor, 109 is a diode bridge, 110 is a dial circuit, 111 is a cross point switch circuit, 112
are number buttons, 113 is a call circuit, and 114 is a transmitter (T
), 115 is a receiver (R), 116 is a processor, 11
7 is a terminal device, 200 is an internal circuit.

Claims (1)

[Claims] A telephone line (2
) is rectified by the diode bridge (109) and connected to the internal circuit (200).
In the telephone terminal device (1), a part of the diodes constituting the diode bridge (109) is constituted by a diode section of a photocoupler (106), and the output signal (d) of the photocoupler (106) A polarity reversal detection method characterized by detecting polarity reversal of a DC power source (100).