GB944002A - Fault locating circuit arrangement - Google Patents

Abstract

944,002. Line transmission systems; repeater fault locating. STANDARD TELEPHONES & CABLES Ltd. May 9, 1962, No. 17856/62. Heading H4R. In a fault locating circuit arrangement for a system in which the power supply circuits for a number of repeaters, C and E, Fig. 1, are connected in series with a common source of power 3, a slow acting relay at each repeater has its winding 5 connected in the power supply circuit and its normally closed contacts 8 connected across the circuit on the side of the repeater remote from the power source. To find the location of a fault, power is applied to the circuit at terminals 3 and a signal source across terminals 10. After a time, sufficient to allow the amplifiers in the repeater to warm up and the signal applied to terminals 10 to be transmitted via repeater C and contacts 8 back to an indicator 12, relay 5 operates and contacts 8 open and allow power to be transmitted to the following repeater E where a similar process occurs. The voltage across the constant current source 3, read on meter 9, indicates how many repeaters are in circuit while the burst of signal received at indicator 12 during the time between the warming up of each repeater and the opening of the contacts 8 associated with each repeater indicates the correct functioning of the amplifiers in that repeater. A preferred method of obtaining the delay in operation of relay 5 is illustrated in Fig. 3 in which a constant voltage source to supply the repeater amplifier is established across an avalanche type diode 14. The relay coil 5, in series with a thermistor 13 is connected across the stabilised supply with the heater of the thermistor connected across a low resistance 15 in series with the diode.