JPS5837744B2 - Loopback control method and device in PCM transmission line - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for controlling loopback in a PCM relay transmission line.

In a system using a PCM transmission line with a loop-shaped line, such as a PCM data highway system, if a failure such as a disconnection occurs in the transmission line, conventionally the end station equipment will The line was maintained by looping back and creating new loops.

This is because, in this type of PCM transmission line, power is generally supplied to a repeater provided in the middle of the line via the center of gravity line, and unless a loop is formed, power cannot be supplied.

FIG. 1 schematically represents the conventional PCM transmission system as described above, in which 10 is a central terminal equipment, 12 is an information processing device that controls the central terminal equipment 10,
14.16 is a repeater, 18.20 is a remote terminal equipment, 22
, 24 represent a group of terminal devices connected to each remote terminal device 18, 20, respectively.

These repeaters 14, 16 and remote terminal equipment 18, 20
are connected in a loop with respect to the central terminal equipment 10 via the PCM working line 26.

Further, a PCM protection line 28 is also connected in a loop along the working line 26.

When a transmission line disconnection occurs at, for example, a portion 30 of such a transmission line, conventionally, the terminal equipment 1B, 20 connects the working line 26 and the protection line 2B to perform a loopback.

However, with this type of loopback method, a worker must go to the end station where the disconnection occurred and perform the loopback operation, which requires a lot of time for temporary recovery. I had a problem.

Therefore, the present invention solves the above-mentioned problems of the prior art, and an object of the present invention is to provide a loopback control method and apparatus that can automatically perform loopback by controlling from a central terminal station. It is about providing.

A feature of the present invention that achieves the above-mentioned object is that an independent control line is provided along the transmission line, and a plurality of loop control units are also provided separately along the transmission line, and the loop control unit section connects the control line with the control line. While sequentially connecting the working line and the control line, check whether the working line and the control line can be connected to the central terminal station in a loop, and check if the loop control unit is connected to the central terminal station in a loop. The main feature is that the loop control unit located farthest from the central station equipment on the transmission path connects the working line and the protection line, that is, performs loopback.

The present invention will be explained in detail below using Examples.

FIG. 2 is a structural diagram of one embodiment of the present invention.

In the figure, 32 is a central terminal equipment, 34, 36
1 shows a PCM working line N and a PCM protection line E that connect each terminal station in a loop with respect to the central terminal station device 32.

In the middle of each line are PCM repeaters REP38-1 to 38,4 (L, to 40-n) that are powered by the center of gravity line.
Although not shown, a remote terminal device is provided.

A control line 42 independent from these lines is provided along the working line 34 and the protection line 36, and this control line 4
2, there are loop control units 44-1 to 44-n.
are inserted with appropriate spacing between them.

Since these loop control units 44-, 44-o and their surrounding parts have the same structure, they will be referred to as 44-1 below.
The structure of only the unit part will be explained.

The loop control unit 44-1 uses the nearby working line 34.
It is connected to via a normally closed relay contact 46a.

The other end of this contact 46a is connected to the control line 42 through one-way current detectors 48, 50-1 connected in parallel in opposite directions.
Bidirectional current detectors 52, 5t1 are inserted and connected to the control line 42 on both sides of the connection point C.

The detection outputs S and S4 of the current detectors 48-1 to 54-1 are applied to a logic circuit 56, and the output of this logic circuit 56 is applied to the normally closed relay drive unit 46b and the drive circuit 58b of the loopback switch 58a. It is configured to be sent.

The loop pack switch 58a is the loop control unit 4
This is a switch that enables electrical connection between the working line 34 and the protection line 36 in the vicinity of 4-1, and a similar switch is provided for each loop control unit section.

The central terminal device 32 includes a constant current supply source 60 whose positive and negative poles are connected to both ends of the working line 34, and a control line 42.
A loop test switch 62 is provided for selecting whether to connect to the positive or negative electrode of the constant current supply source 60, or to leave it unconnected to either.

Loop control unit}44-1 current detection b4B-
t to 54-1 are constant voltage types configured to detect current when a certain voltage or more is applied to both ends, and to prevent the terminal voltage from rising above the certain voltage when detected. This is a current detector.

FIG. 3 shows an example of this type of current detector, and A is a circuit example of unidirectional current detectors 48-1 and 50-1, and B is a circuit example of bidirectional current detectors 52-1 and 54-1.

In Figure 3A, 64.66 is a constant voltage diode, 6
8 indicates a photocoupler.

The voltage applied between the terminals 70a and 70b is the Zener voltage of the constant voltage diode 64.

If it is smaller, a current flows through the light emitting diode of the photocoupler 68 and the photodiode is turned on, so that the detection outputs S1 and S2 become low level.

The voltage between terminals 70a and 70b is ■.

When the value exceeds 0, the Zener current starts to flow, so the current of the photocoupler 68 is cut off, and thus the detection outputs S1 and S2 become high level.

Also, as a matter of course, the voltage between the terminals 70a and 70b is this Zener voltage ■.

It doesn't get bigger.

However, the above explanation is based on the case where the forward voltage drop of the voltage regulator diode 66 is ignored.

This constant voltage diode 66 is provided to achieve a similar constant voltage operation when a voltage in the opposite direction to that described above is applied between the terminals 70a and 70b.

The circuit in Figure 3B is designed to perform the same operation as the circuit in Figure 3A for applied voltages of both polarities, and the difference between the two is that the circuit in Figure 3B is newly designed. Photo coupler 72
is connected in parallel to both ends of the constant voltage diode 66 in FIG. 3A.

Therefore, a description of its operation will be omitted.

FIG. 4 is a block diagram showing an example of the logic circuit 56 in the loop control unit 1-44.

In the same figure, 74, 76, 78, 80 are current detectors 4
Detection output S of EL1, 5 (L1, 511, 54-,
1, S set at the rising edge of S2, S3, S4
-R flip-flop, 82 is an OR gate, 84 is a transistor switched by the output of the OR gate 82, 46b is the above-mentioned normally closed relay drive section, 86.8
8 is an AND gate that takes the AND of the outputs of flip-flops 80 and 74 and flip-flops 76 and 78, respectively; 90 is a timer circuit that generates an output (talok pulse) after a predetermined time delay from the output of OR gate 82; 92
is a delay circuit that gives an appropriate delay to the output of the timer circuit 90 to form a pulse that resets the flip-flops 74 to 80, and 94 and 96 are the output states of the AND gates 86 and 88 when the output of the timer circuit 90 is applied. Each figure shows a clocked flip-flop whose output logic is determined according to the output logic.

The outputs of flip-flops 94,96 are arranged to be sent to drive circuit 58b shown in FIG.

Next, the operation of this embodiment will be explained.

When a failure occurs in the transmission line, the operator operates the loop test switch 62 of the central terminal equipment 32 to first switch its movable contact to the N/ETST side.

As a result, the current detectors 48-1 and 52-1 in the first loop control unit 44-1 are in the operating state, that is, in a constant voltage state where the Zener current flows, and the current is a-+c-
Flows in a +b loop.

Then, the detection outputs S1 and S3 are inverted to high level.

In this case, the voltage between a4-+c is the Zener voltage ■.

Therefore, the loop control unit 44 of the next stage and subsequent stages
-2... Current detectors 48-2... and 52
-2... is not in the operating state.

By the way, in order for the next-stage current detector 48-2 to operate, including the operation requirements of the current detector 54-1, a4-) C
It is necessary to apply a voltage of 3μ or more between them.

When the detection output S1 becomes high level, the flip-flop 7
4 is set, and the transistor 84 is turned on by its Q output.

As a result, the normally closed relay drive section 46b is energized and the normally closed relay contact 46a is opened.

When the contact 46a opens, the next loop control unit 44-2
If there is no abnormality in the working line 34 up to, this unit 4
The current detectors 48-2 and 52-2 of 4-2 are activated, and the current detector 54-1 of the loop control unit 44-1 in front of them is activated, and the detection output S4 becomes high level.

As a result, flip-flop 80 is set in loop control unit 44-, and the output of AND gate 86 goes low.

The timer circuit 90 provides a delay time that is slightly longer than the elapsed time from when the current is detected in the loop control unit 1-44 until the current is detected in the next loop control unit 44-2. Therefore, in the above case, after flip-flop 80 is set, a clock pulse is output to clocked flip-flop 94.

Since the AND gate 86 outputs a low level, the output of the flip-flop 94 becomes a low level, and the loopback switch 58a remains open in this case.

Thereafter, if there is no abnormality in the working line 34, similar operations are sequentially performed in each loop control unit 44-2, 44-8, . . . .

Now, assuming that the working line 34 between the loop control units 44-1 and 44-2 is disconnected, the current detector 5
4-1 is not activated, and the detection output S4 remains at a low level.

As a result, flip-flop 80 is not set and the output of AND gate 86 goes high.

Therefore, when a clock pulse is applied from the timer circuit 90 after a predetermined period of time, the output of the flip-flop 94 becomes high level, the drive circuit 58b is energized, the loopback switch 58a is closed, and the working line 34 and the protection line 36 are connected to each other.
is electrically connected at this point, and a loopback operation in which power is supplied from the working line to the protection line, that is, an N/E loopback operation, is automatically performed.

The operator then turns the loop test switch 62 to E/NT.
When switching to the ST side, an E/N loopback operation is automatically performed in the same manner as the above-mentioned N/E loopback operation.

As explained in detail above, according to the present invention, the loopback operation can be automatically performed by operation from the central terminal station. Therefore, when a failure occurs in a transmission line, it can be quickly temporarily restored, and the work required for that purpose can be significantly reduced.

Therefore, if the present invention is applied to a PCM transmission line, there will be great industrial advantages.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining conventional loopback operation, FIG. 2 is a structural diagram of an embodiment of the present invention, and FIGS. 3 and 4 are partial diagrams of the embodiment of FIG. 2. It is a circuit diagram. 32...Central terminal equipment, 34...PC
M working line, 36...PCM protection line, 38-
1 to 38, 40-1 to 40-n...PCM
Repeater, 42... Control line, 44-1 to 44-
n...Loop control unit, 46a...
- Normally closed relay contact, 46b... Normally closed relay drive section, 4B-1, 5 (L1... One-way current detector, 52-1, 54-1...・Bidirectional current detector,
56...Logic circuit, 58a...Loopback switch, 58b...Drive circuit, 60
... Constant current supply power supply, 62 ... Loop test switch, 64, 66 ... Constant voltage diode, 68, 72 ... Photo coupler, 74, 76
,78.80...SR flip-flop, 82
...OR gate, 84...Transistor, 86,88...AND gate, 90...
...Timer circuit, 92...Delay circuit, 94,
96...Clocked flip-flop.

Claims (1)

[Scope of Claims] 1. In a loopback control method for a PCM transmission line including a working line and a protection line each formed in a loop with respect to a central terminal station, a control line separate from each line is connected to the transmission line. At the same time, a plurality of loop control units are arranged at intervals along the transmission line, and when a failure occurs on the transmission line, the working line and the control line are successively connected at each control unit section. By checking whether or not an electrically closed loop is formed between the working line and the control line with respect to the central terminal station, the control unit that has been able to form a closed loop and is located farthest from the central terminal station on the transmission path. 1. A loopback control method in a PCM transmission line, characterized in that the working line and the protection line are electrically connected in the section. 2. The control method according to claim 1, wherein the conduction between the working line and the control line is performed sequentially from a control unit located close to the central terminal station on the transmission path. 3. In a loopback control device for a PCM transmission line, each of which is provided with a working line and a protection line formed in a loop with respect to a central terminal station, a control line and a control line arranged along the transmission line separately from each of the lines. , a plurality of loop control units that are spaced apart along the transmission path and are capable of establishing continuity between the working line and the control line, and each loop control unit electrically connects the working line and the protection line. and a plurality of switches that can be connected to each other, and each of the loop control units sequentially connects adjacent loop control units when an electrically closed loop of the working line and control line to the central terminal station is formed by the conduction thereof. Loopback control in a PCM transmission line, comprising a continuity control circuit and a switch control circuit that energizes the corresponding switch when the next loop control unit does not establish the closed loop. Device. 4. Claim 3, wherein each of the conduction control circuits is provided with a switch circuit that becomes conductive and immediately cuts off the conduction when a voltage of a predetermined value or higher is supplied between the working line and the control line. Control device as described. 5. The control according to claim 3 or 4, wherein each conduction control circuit includes a circuit that prohibits conduction in other loop control unit sections when conduction occurs in the loop control unit section. Device. 6. Claims 3 and 4, wherein the switch control circuit energizes the switch only when conduction does not occur in the next loop control unit after conduction occurs in the loop control unit. or the control device according to item 5.