GB472806A - Improvements in or relating to high-frequency carrier-wave transmission systems - Google Patents

Abstract

472,806. Repeating systems. STANDARD TELEPHONES & CABLES, Ltd. April 7, 1937, No. 9918. Convention date, April 7, 1936. [Class 40 (iv)] In a multiplex carrier-wave system employing separate coaxial cables for the two directions of transmission, signalling between unattended and attended repeater stations is effected by low-frequency currents transmitted over the central conductors of the two cables in series. Feed current for the unattended repeaters is transmitted over the same circuit. In the system shown, 16-cycle feed current is connected through a transformer 38 and filters 18, 19 to the central conductors of the cables 12, 13 and is fed off through similar filters at the first unattended station R1 to a power-supply unit 21 and through byepass circuits 59, 60 to a second unattended station R2. At each unattended station the cables have contact devices 29 controlled by gas-pressure in the cable and when this falls below a certain value the closure of one of the contacts completes a circuit through filters 43, 18, 19 and the central conductors of the cables for an alarm indicator 27, the signalling circuit being fed with 2000- cycle current over a transformer 45. To locate the fault, switch 54 is closed to shortcircuit the indicator and an appropriate reading is given on an ammeter 52 controlled by a thermocouple 51. Telephonic communication between the stations may be obtained by throwing key 41 and plugging into jack 66. Modifications are described for giving constant-current and constant-voltage power supply to the unattended repeaters.