| 摘要 |
<p>914,788. Feeding and supervising unattended repeaters. BRITISH TELECOMMUNICATIONS RESEARCH Ltd. Oct. 27, 1960 [Nov. 6, 1959], No. 37765/59. Class 40 (4). In a carrier telecommunication system in. cluding a plurality of repeaters fed in series by a constant direct current source over the signalling circuit, a relay in each repeater when first operated by the D.C. disconnects a resistor from across the D.C. feed circuit, the values of the resistors progressively increasing for each repeater so that the relays operate in sequence. The values of the resistors RA1, RB1, &c. are chosen so that on applying .current to the central conductors of coaxial cables +, - leading to the repeaters AP1, AP2, &c. from a terminal station BN, initially only sufficient current is available for operating relay A. This open circuits resistor RA1 so that more current is available for relay B which then pulls up and so on. This occurs as far as the turn-round point indicated by choke CH1, further repeaters being put into operation using a similar technique from terminal station CH. Two communication systemsα, # each employing separate cables for the GO and RETURN paths, have a common supply system. Each path includes gain regulators, e.g. GN controlled by a pilot signal and in the event of a regulator being required to adjust the gain by more than a predetermined amount, i.e. due to some failure in one of the transistorized repeaters preceding it in the GO path, a relay operates which at contactsα1 (corresponding to GO path from BN) orα2 (from CH) puts a resistor of characteristic value across supervisory leads BC (lead A being connected to lead B through resistor R, Fig. 4). A milliameter (not shown) is connected to lead B and an alarm relay (not shown) is connected to lead C, the meter being calibrated so that the section in which the faulty repeater lies can be read off directly. If a line fault should occur, e.g. a break between repeaters AP2, AP3 in the GO path, relays A-F will drop out and then since the original conditions exist, i.e. resistors RA1 &c. in circuit, relays A, B will re-energize but now relay C cannot operate and hence at contacts C2, a characteristic resistor RC2 is connected across supervisory leads B and D. An alarm is given as indicated above. If the repeaters are contained in pressurized containers then a loss of pressure is indicated by the closing of contacts GAS1, GAS2, &c., which introduce further characteristic resistors across supervisory leads B and D.</p> |
