Patent GB-456993-A (GB)
Title: Improvements in or relating to submarine electric cable systems
IPC: H03F1/54
Filed: 1935-05-31
Abstract: 456,993. Submarine cable systems. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.- (Assignees of Gannett, D. K. ; 3722, 85th Street, Jackson Heights, New York, U.S.A.) May 31, 1935, No. 15863. Convention date, June 2, 1934. [Class 36] [See also Group XXXIX] A submarine cable system comprises a multi-conductor paper insulated cable 2, Fig. 1, supported below the surface of the sea at such a depth that the effects of surface currents and waves are inappreciable by a messenger wire 1 which carries a series of buoyant devices 4 and which is anchored to the sea bed by widely spaced anchors 7. The anchors 7 are connected by wires 8 to inverted catenary wires 5 which are attached to the messenger wire by vertical wires 6. The system may include one or more repeaters 9 which are submerged to the same depth as the cable, the connection between the repeater and the cable sections such as 19, 20 comprising loops 12 of slack cable sufficient to permit withdrawal of the repeater above the sea surface during servicing. Preferably, the repeater comprises a repeater chamber 11 enclosing the repeating apparatus and its power sources, and a terminal box portion 13 to which the chamber may be readily connected, so that a spare chamber with tested apparatus and fresh power sources may be quickly substituted for the chamber which has been in use. A float 10 increases the buoyancy of the repeater to such an extent that it is easily supported by the messenger wire 1 or by the hoisting cable 17 which connects the repeater to a marking buoy 14. The chamber 11 and terminal box 13 may be filled with nitrogen at a pressure equal to the hydrostatic-pressure at the depth at which the repeater is submerged. Each repeater may comprise several amplifiers any selected one of which may be brought into use as desired, and means may be provided for adjusting the gain of the amplifier in use from the shore terminal. Fig. 3 shows a repeater having ten amplifiers 31 which are controlled by a five pole ten way step-by-step selector switch 32 which permits any one of the amplifiers to be inserted between an incoming pair of conductors 26 and an outgoing pair 27. The input terminals of the amplifiers are connected to contact banks a, b of the switch, the associated switch arms of which connect through conductors 30, gain potentiometer 29 and high-pass filter 28 to the incoming pair 26. The out-going pair are similarly connected through a highpass filter 35, conductors 34 and contacts c, d to the output terminals of the selected amplifier. The power for operating the selected amplifier is supplied from a common source 39 through contacts e of the selector switch. The selected amplifier is brought into circuit by sending pulses of direct current from a source 40 at the shore terminal over the lower conductors 26, 27 which are connected together by chokes 45 and relay 42, the current pulses actuating the relay 4 which controls the stepping magnet 33 of the selector switch. In order to permit adjustment of gain at the repeater an automatic level indicator 46 is provided across the output conductors 34 of the amplifier, the power supply 58 for the indicator being switched into circuit when desired by a relay 61 which is operated by sending direct current from the shore terminal over the upper conductors 26, 27. When it is desired to adjust the gain of the repeater, the relay 61 is operated and a thousand cycle carrier wave with a twenty cycle interruption is applied at the shore terminal to the conductors 26. The amplified thousand cycle wave appearing on the conductors 34 is demodulated by the level indicator 46 which measures the magnitude of the resultant twenty cycle component. If the magnitude of this component is below a predetermined value a relay 49 is energized and closes the circuit of a motor 52 which is arranged to drive the slider 54 of the gain potentiometer 29 in such a direction as to increase the input to the amplifier ; if, however, the magnitude of the detected twenty cycle component exceeds the predetermined value, both relays 48 and 49 are energized thereby closing the circuit of a motor 56 which drives the slider 54 in the reverse direction to the motor 52. The motors 52, 56 drive the slider 54 through magnetic clutches 53, 57. British Specification 229,006, [Class 122 (iii)], and U.S.A. Specification 1,574,808 are referred to.