JPH0441860B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in an outgoing trunk monitoring system for connecting a DC two-wire analog trunk line to an exchange.

On the outgoing trunk that connects the DC two-wire analog trunk line to the exchange, the A from the opposite station when there is no call.
monitor the DC voltage supplied between the line and the B line,
Also, during a call, the normality of the trunk line is confirmed by monitoring the DC current flowing through the DC loop circuit provided between the A line and B line in the outgoing trunk.

When this type of outgoing trunk is installed alongside an electronic exchange, it is desirable to digitize the entire outgoing trunk, including the DC voltage and DC current monitoring section.

[Conventional technology]

FIG. 3 is a diagram showing an example of a conventional outgoing trunk monitoring system.

In Figure 3, when there is no call, transistor 1
and 2 are both in a disconnected state, and only a series circuit of a high resistance 3 of, for example, about 22 kilohms and a photocoupler 4 is connected between the A line and the B line of the outgoing trunk. In this state, when a DC voltage with the A line as the (-) pole and the B line as the (+) pole is supplied from the opposite station between the A line and the B line, the photocoupler 4 is energized and sends out an output signal. do. By monitoring the output signal, it is possible to monitor the direct current voltage supplied to the relay line from the relay line and the opposing station.

On the other hand, during a call, one of transistors 1 and 2 becomes conductive depending on the polarity of the DC voltage supplied from the opposite station, and the voltage is passed through the two-wire side winding 6 of the transformer 5 for two-wire and four-wire conversion. A DC loop circuit is formed between the A line and the B line. In such a case, one of the photocouplers 7 and 8 is energized depending on the polarity of the DC voltage supplied from the opposite station, and sends out an output signal. By monitoring the output signal, it is possible to monitor the DC current flowing through the DC loop circuit using the DC voltage supplied from the opposing station.

[Problem that the invention seeks to solve]

As is clear from the above description, in the conventional outgoing trunk monitoring system, photocouplers 4, 7, and 8 are used to monitor the DC voltage during no calls and the DC current during calls.

However, since photocouplers are not necessarily more reliable than other electronic components, frequent use of photocouplers may reduce the reliability of the outgoing trunk.

In addition, photocouplers do not necessarily have sufficient reverse breakdown voltage, and it is necessary to insert diodes 9 and 10 in series, resulting in an increase in forward voltage drop.
This may have an adverse effect when digitizing a DC loop circuit.

[Means for solving problems]

According to the present invention, the above problem can be solved by using one differential differential in order to monitor the combination of DC voltage and polarity change between the A and B lines in the outgoing trunk connected to the two-wire analog trunk line consisting of the A and B lines. In a differential amplifier including an amplifier 12 and a plurality of comparators, and a resistor connected between an inverting input terminal and an output terminal, the AB line voltage is compressed to within the operating voltage range of the differential amplifier and output. As shown in FIG. The output voltage of the differential amplifier is applied to one terminal of each of the plurality of comparators, and the other terminals of the comparators each correspond to a different reference voltage formed using the set voltage as a reference. The problem is solved by an out-trunk monitoring scheme, which is characterized in that the combination of the outputs of the comparators is used to identify different combinations of voltage and polarity changes between the AB lines.

[Effect]

That is, according to the present invention, the DC voltage and DC current monitoring circuit includes a differential amplifier that compresses the AB line voltage and maintains it within a predetermined voltage range, a set voltage generation means that determines the operating point of the monitoring circuit, and AB
Consists of multiple comparators that compare combinations of line voltage and polarity with reference voltages, eliminating the need for photocouplers and making direct current monitoring possible.
Since the voltage between the line and the B line is monitored, there is no need to insert a diode or the like in series with the DC loop circuit, and it is also effective in computerizing the DC loop circuit.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an outgoing trunk monitoring system according to an embodiment of the present invention, and FIG. 2 is a diagram showing an example of voltage changes between the A line and the B line in FIG. 1. Note that the same reference numerals indicate the same objects throughout the figures.

In Figure 2, when there is no call (period T1) and the trunk line is normal, the opposite station connects the A line to the (-) pole (for example -48 volts) and the B line to the (+) pole (for example, ground). A DC voltage _VB is supplied, and the voltage _VAB applied between the A line and the B line of the outgoing trunk is approximately equal to _VB .

Next, the outgoing trunk calls state, and the A line and B line
When a DC loop circuit (not shown) is formed between the lines (period T2), the output trunk AB line voltage V _AB is
The voltage drops to V _AB ′, which is caused by the flow of DC current in the DC loop circuit.

Furthermore, when the called party answers and the call state is established (period T3), the polarity of the DC voltage supplied from the opposite station is reversed, so the AB line voltage V _AB of the outgoing trunk becomes −V _AB ′, that is, the period T3. The absolute value is the same as in the case of T2,
The polarity is reversed.

Next, when the called party recovers (period T4), the polarity of the DC voltage supplied from the opposite station is reversed again, so the outgoing trunk AB line voltage V _AB becomes V _AB ', as in period T2.

Next, when the outgoing trunk enters the recovery state (period T
5) Since the DC loop circuit formed between the A line and B line is opened, the voltage between the A and B lines of the outgoing trunk
V _AB is approximately equal to V _B , similar to period T1.

Next, when the opposite station requests blocking of the trunk line (period T6), the polarity of the DC voltage supplied to the trunk line in the no-call state is reversed. As a result, the output trunk AB line voltage V _AB becomes approximately equal to -V _B. In such a state, it is necessary for the outgoing trunk to block the relevant trunk line to prevent outgoing calls.

Next, if the trunk line is in an abnormal state and the DC voltage supplied from the opposite station between the A and B lines of the trunk line is not transmitted to the outgoing trunk, or the opposite station is in an abnormal state and the DC voltage supplied between the A and B lines of the trunk line is When no DC voltage is supplied between the B lines (period T7), the output trunk AB line voltage V _AB generates only a small voltage such as noise. In such a case, it is necessary for the outgoing trunk to block the relevant trunk line to prevent outgoing calls.

In FIG. 1, the set voltage V _C is set approximately midway between the DC power supply voltage of the own station and the ground voltage, and is connected to the differential amplifier 12 and each comparator 1 via the emitter follower 11.
3 to 15. The output trunk AB line voltage V _AB is transmitted to the inverting input terminal (−) and non-inverting input terminal (+) of the differential amplifier 12 via resistors 16 and 17 . By setting the resistance values of resistors 18 and 19 to an appropriate ratio (for example, 1/7) to the resistance values of resistors 16 and 17, the AB line voltage V _AB that changes as shown in FIG. , are compressed to a DC voltage that does not exceed the allowable range of the operating voltages V+ and V- of the differential amplifier 12. Furthermore, by connecting diodes 20 to 23 between the inverting input terminal (-) and non-inverting input terminal (+) of the differential amplifier 12 and the operating voltages V+ and V-, the inverting input terminal of the differential amplifier 12 (-) and non-inverting input terminal (+) with operating voltage V
This prevents voltages outside the range of + and V- from being applied.

The voltage compressed by the differential amplifier 12 is further converted into a set voltage transmitted from the emitter follower 11.
It is superimposed on V _C and output as a superimposed voltage V _O from the output terminal O of the differential amplifier 12, and is input to each non-inverting input terminal (+) of the comparators 13 to 15.

The difference voltage between the set voltage V _C and the operating voltage V+ is connected to the inverting input terminal (-) of the comparator 13 through the resistor 24.
and the reference voltage generated by dividing the voltage by 25
V _r1 is the inverting input terminal (-) of the comparator 14, and the difference voltage between the set voltage V _C and the operating voltage V+ is
The reference voltage V _r2 generated by dividing the voltage by the resistors 26 and 27 is further inputted to the inverting input terminal (-) of the comparator 15 by the difference voltage between the set voltage V _C and the operating voltage V-, which is generated by the resistors 28 and 29. The reference voltage V _r3 generated by voltage division is inputted. The reference voltage V _r1 is set to distinguish between the superimposed voltage V _O in periods T1 and T5 and the superimposed voltage V _O in periods T2 and T4, and the reference voltage
V _r2 is the superimposed voltage V _O in periods T2 and T4
The reference voltage V _r3 is set to distinguish between _{the superimposed voltage V O in} the period T3 and T6 and the superimposed voltage V _O in the period T7. .

As a result, during periods T1 and T5, that is, when the trunk line is normal and there is no call, the comparators 13 to 15 output output signals, and during periods T2 and T4, that is, when the outgoing trunk is in the calling state and the called party answers. If not, comparators 14 and 15 output output signals;
In addition, during period T7, that is, when the power supply of the trunk line or the opposite station is in an abnormal state, only the comparator 15 outputs an output signal, and further during periods T3 and T6, that is, when the outgoing trunk is in the calling state, the called party If the station is responding, and if the opposite station is requesting closure of the trunk line, all the comparators 13 to 15 do not output any output signals. Note that the period T3 and the period T6 can be distinguished depending on whether or not the outgoing trunk is in a calling state.

As is clear from the above description, according to this embodiment, the outgoing trunk AB line voltage V _AB is divided by the differential amplifier 12, and further superimposed on the set voltage V _C transmitted from the emitter follower 11 to create a superimposed voltage. V _O
By converting the voltage into 100% and monitoring it using comparators 13 to 15, there is no need to use a photocoupler, and monitoring of the DC current can be replaced with monitoring of the AB line voltage V _AB . There is no need to insert a diode, etc., and it is also effective for computerizing DC loop circuits. Furthermore, since it targets the AB line voltage V _AB , it is not affected by the ground potential difference with the opposite station, and the
By inserting this, the high voltage generated in the A and B lines of the relay line can be sufficiently protected.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to monitor the normality of the trunk line in the outgoing trunk without using a photocoupler or inserting a diode or the like in series with the DC loop circuit. Not only is it effective in reducing the power consumption, but it is also unaffected by the difference in ground potential with the opposite station, and is sufficiently protected against high voltages occurring in the A and B lines of the trunk line.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an outgoing trunk monitoring system according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of voltage change between the A line and B line in FIG. 1, and FIG. 3 is a diagram showing a conventional outgoing trunk monitoring system. FIG. 3 is a diagram illustrating an example of a monitoring method. In the figure, 1 and 2 are transistors, 3,
16 to 19 and 24 to 29 are resistors, 4, 7
and 8 is a photocoupler, 5 is a transformer, 6 is a two-wire side winding, 9, 10 and 20 to 23 are diodes, 11 is an emitter follower, 12 is a differential amplifier, 13 to 15 is a comparator, and V _AB is an output trunk.
AB line voltage, V _B is the DC voltage of the opposite station, V _C is the set voltage, V _O is the superimposed voltage, V _r1 to V _r3 are the reference voltages,
shows.

Claims (1)

[Claims] 1 In order to monitor the combination of DC voltage and polarity changes between the AB lines in the outgoing trunk connected to the two-wire analog trunk line consisting of the A and B lines, one differential amplifier 12 and multiple comparisons are used. In a differential amplifier in which a resistor is connected between the inverting input terminal and the output terminal, the B line is compressed and output within the operating voltage range of the differential amplifier. The A line is connected to the inverting input terminal via a resistor, and the A line is connected to the non-inverting input terminal via the resistor, and a set voltage for setting the operating point of the monitoring circuit is connected to the non-inverting input terminal via the resistor. The output voltage is applied to one terminal of each of the plurality of comparators, and different reference voltages formed based on the set voltage are applied to the other terminals of the comparators. An outgoing trunk monitoring method characterized by identifying combinations of different voltages and polarity changes between AB lines.