| 摘要 |
<p>992,690. Unattended repeaters. GENERAL ELECTRIC CO. Ltd. Sept. 28, 1961 [Oct. 4, 1960], No. 33992/60. Heading H4R. A repeater which is supplied with operating current over the transmission path, has associated therewith a first path which by-passes the repeater and a second path which is connected across the power supply conductors, the arrangement being that both paths offer a high resistance to supply current during normal operation but offer a lower resistance under " fault conditions." The latter are defined as an open-circuit repeater or a change in a parameter of the current supplied to the repeater, e.g. reverse battery. In Fig. 1, a number of repeaters 1, 2 are shown connected in a two-wire line 7, 8 carrying multi-channel carrier signals between terminal stations 5, 6. During normal operation, constant current source 11 supplies power to the line, rectifiers 25 are non-conducting and Zener diodes 24 are just conducting in the reverse direction. If repeater 1, say, develops an open-circuit, its Zener diode 24 breaks down completely so that the current supply for subsequent repeaters is maintained and the fault is signalled to station 6 using the system described in Specification 853,884. If an open-circuit occurs between repeaters 1 and 2, say, the cessation of current in the system initiates alarms at station 5. The location of the fault is achieved by applying constant voltage source 31 (of opposite polarity to the current source) to the line so that rectifier 25 conducts and with a knowledge of the resistance of the line and the reading on ammeter 32 the location of the fault can be deduced. For a short circuit or an earth fault in a repeater or the line, the output voltage of source 11 will fall and so initiate an alarm, the magnitude of the potential " loss " being an indication of the position of the fault. A four-wire system in which the phantom of the GO and Return paths is used both for audio-frequency signalling and the power supply is described with reference to Fig. 2 (not shown). A system in which a relay is connected in series with each repeater amplifier and has two contacts which replace the rectifier and Zener diode respectively is described with reference to Fig. 3 (not shown).</p> |
