JPS6126629B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention detects whether or not a fault has occurred between the near end (as seen from the station side) and far end of a pair cable in a communication system that allows communication without DC power supply. This relates to a fault detection method.

FIG. 1 is a schematic diagram showing a conventional fault detection method, and FIG. 2 is a schematic diagram showing a case where a cable is short-circuited in such a fault detection method.

Please refer to FIG. In the figure, 1 is a pair cable, 2 is a connecting conductor, 3 is a DC power supply,
4 indicates an ammeter.

Now, in Figure 1, for each pair cable,
When trying to detect whether a fault has occurred between the near end and far end, a line maintenance person goes to the far end and
While consulting with the line maintainer on the near-end side, connect both terminals on the far-end side of the pair cable to each other using connecting conductor 2, apply DC power 3 from the near-end side, and at this time, connect cable 1 to By measuring the flowing DC power with an ammeter 4, the loop resistance value of the cable was determined, and then compared with the loop resistance value recorded at the time the pair cable was laid, an abnormal difference was detected between the two. If so, it was determined that a break or short circuit had occurred in the pair cable. However, as shown in Figure 2, when both wires of the pair cable 1 are short-circuited near the far end, the fault detection method explained with reference to Figure 1 can determine whether a short-circuit fault has occurred. , I can't tell if it's normal or not.
Therefore, in such a case, conventionally, a line maintenance person on the far end side opens both terminals of the cable on the far end side and measures the line capacitance. That is, the capacitance value when the far end side of the pair cable 1 is open is determined. Then, as described above, a comparison is made with the capacitance value measured at the time the pair cable was laid, and whether or not a failure has occurred is determined based on whether an abnormal difference is detected between the two.

As mentioned above, in the conventional fault detection method,
The line maintenance person goes to the far end side, has a meeting with the line maintenance person at the near end side, measures the loop resistance value or capacitance value, and compares it with each measurement value at the time of cable installation to determine whether there is a pair cable failure. In addition to requiring the labor of maintenance personnel to visit the site, there were other inconveniences such as losing measurement records from the time the cable was laid, which would impede failure detection.

This invention was made in order to overcome the disadvantages of the conventional system as described above, and the purpose of this invention is to eliminate the need for line maintenance personnel to go to the far end of the cable, and to eliminate the need for line maintenance personnel to go to the far end of the cable. The object of the present invention is to provide a method for detecting faults in paired cables that does not require reference to records of cables.

The gist of the configuration of the present invention is that in a communication pair cable that can communicate without requiring DC power supply, there is a means for applying DC power to the near end thereof, and a means for applying DC power to the far end by applying the DC power. a switching means for connecting cables and repeating the disconnection; a means for detecting a pulsating signal generated by the disconnection at the near end; and a means for detecting a pulsating signal generated by the disconnection at the near end; The point is that means is provided for cutting off the circuit in the form of direct current at the far end so that no voltage is applied to connected equipment.

Next, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 3 is a schematic diagram showing an embodiment of the present invention. In the figure, 6 is the excitation winding of the relay, 6a is its contact, and the capacitor 8 is used to apply direct current across the far end of the pair cable to equipment (such as a telephone) connected to the far end. This is to cut off the circuit in direct current so that the equipment will not be damaged. 7 is a pulsation signal detector.

Next, the operation will be explained. In FIG. 3, a DC power source 3 is applied to the near end, thereby exciting the excitation winding 6 of the relay at the far end via its contacts 6a. Note that the capacitor 8 interrupts the circuit in terms of direct current so that direct current does not flow beyond the far end to equipment (not shown) connected to the far end. This is because the pair cable 1 belongs to a communication system that allows communication without DC power supply, so no DC is normally applied. This is to prevent equipment connected to the far end from being damaged by the application of direct current when direct current is applied to detect a fault.

Now, when the excitation winding 6 is excited, it opens the contact 6a. Then, the excitation winding 6 is de-energized and the contact 6a is closed. There, the excitation winding 6 is again excited. In this way, as long as the DC power source 3 is applied to the near end side, the contact 6a repeats opening and closing, generating a DC pulsating signal in the loop circuit of the cable 1. This pulsating signal is detected by the detector 7 via the resistor R. When the detector 7 detects the pulsating signal in this way, it can be determined that the pair cable 1 has no fault. If a short circuit 5' (or disconnection) occurs in the pair cable 1, the detector 7 will of course not be able to detect the pulsating signal, so it is possible to know that a fault has occurred.

FIG. 4 is a schematic diagram showing another embodiment of the present invention, but when compared with FIG. 3, the only difference is the insertion position of the contact 6a, and the other configurations and operations are exactly the same. There is no need to elaborate. It goes without saying that in FIGS. 3 and 4, the switching means can be constructed electronically by using a semiconductor switching circuit in place of the excitation winding 6 and the contacts 6a.

As explained above, the paired cable failure detection method of the present invention has the advantage of simplifying maintenance because it eliminates the need for maintenance personnel to visit the far end side each time a test is performed. Another advantage is that faults can be detected regardless of measurement records at the time of installation.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a conventional pair cable fault detection method, Fig. 2 is a schematic diagram showing a case where the cable is short-circuited in such a fault detection method, and Fig. 3 shows an embodiment of the present invention. Schematic diagram, FIG. 4 is a schematic diagram showing another embodiment of the present invention. In the figure, 1 is a pair cable, 2 is a short-circuit conductor, 3 is a DC power supply, 4 is an ammeter, 5 is a short-circuit point,
6 is an excitation winding of the relay, 6a is a contact, 7 is a pulsation signal detector, and 8 is a capacitor.

Claims (1)

[Claims] 1. A fault detection method for a pair cable that detects the presence or absence of a fault between the near end and far end of a communication pair cable that allows communication without requiring DC power supply. means for applying DC power to the cable; switching means for connecting the cables at the far end and repeating the disconnection by applying the DC power; and detecting a pulsating signal generated by the disconnection at the near end. and means for DC-blocking the circuit at the far end so that the DC power applied from the near end is not applied beyond the far end to equipment connected to the far end. A failure detection method for paired cables.