Patent GB-1388553-A (GB)
Title: Supervisory systems for telecommunication line transmission  system
IPC: H04B17/40
Filed: 1971-05-20
Abstract: 1388553 Digital transmission; testing repeaters PLESSEY TELECOMMUNICATIONS RESEARCH Ltd 27 July 1972 [20 May 1971] 16141/71 Headings H4R and H4P A supervisory arrangement, for use in a system handling digital traffic transmitted using a disparity displaying digital code, which system includes a transmitting terminal, a receiving terminal and a plurality of dependent repeaters connected thereinbetween; includes an interrogation signal generator means located in said receiving terminal arranged periodically to inject an interrogation signal into the transmission system in the opposite direction to the direction of traffic transmission and each dependent repeater is provided with regenerator means arranged to generate a supervisory signal for transmission to said receiving terminal in the direction of traffic transmission and to regenerate the interrogation signal for transmission onward in the direction opposite to that of the traffic transmission, the arrangement being characterized in that each dependent repeater includes a traffic regenerator fault detection means which produces a regenerator fault indication signal and a regnerator fault-free indication signal and these indication signals are active upon the regenerator means to control respectively the selection of one or other of two predetermined characteristic form supervisory signals. The transmitting terminal, the receiving terminal and any intermediate power feed terminals are arranged to transmit a plurality of signals in addition to, and following, said one or other of two predetermined characteristic form supervisory signals, the presence or absence of one or more of the plurality of signals being indicative of the function or non- function of a particular part of the respective terminal. The receiving station (Fig. 1, not shown) transmits an interrogation signal burst in the frequency range below 12 KHz along the incoining -transmission line. This signal is received at the first dependent repeater (Fig. 2). This signal is received by regnerator RLFR via filters F16, and F15 and after a delay is transmitted on via filters F17, F12 to the next repeater. The receipt of this signal causes either a 45 KHz, no fault, or 55 KHz, fault, signal burst to be transmitted from RSPG via gate RGT, filters F14, F15 and the transmission line back to the receiving terminal in the direction of traffic transmission. Which signal is transmitted depends on the signal output of the traffic signal regenerator RDR. Each low bit binary traffic signal is transmitted as one of two ternary signals. e.g. the bit 1111 may be transmitted as 00+ or as -00 (Fig. 4, not shown), and the system is arranged that in any stream of signals, the total number of positives "+" minus the total number of minuses "-" never exceeds Œ4. The repeater error detector RED essentially keeps account of the above numbers and a fault signal of 55 KHz is transmitted, or interrogation, if the number Œ 4 is exceeded. The filters F13, F14 and amplifier RSA constitute a repeater traffic regenerator bi-pass loop for supervisory signals being transmitted back from dependent repeaters further down the line. The transmitting terminal, the receiving terminal and any intermediate power feed terminals also transmit a series of 45 KHz signal bursts to indicate the state of other equipment. A missing burst indicating a fault in a particular sub system of the equipment. The receiving station is equiped with two counters, one which counts 55 KHz signals and one which counts both 45 KHz and 55 KHz signals. By monitoring the counters it is possible to identify the particular faulty repeater or terminal together with the faulty equipment.