GB1212603A - Systems for remotely controlled switching - Google Patents

Abstract

1,212,603. Testing repeaters. HASLER A.G. 8 Feb., 1968 [10 Feb., 1967], No. 6425/68. Heading H4R. In a system for remotely monitoring repeaters, each repeater includes a test oscillator and each oscillator is connected in series in a common constant current power supply lead with a respective switch connected across the oscillator to render the oscillator inoperative when the switch is closed. The switches are operated in sequence by a control line extending from a variable voltage source to each switch circuit. Each switch circuit includes a comparator which compares the voltage on the control line with the voltage on the power supply lead at that relay and opens the switch, to enable the oscillator, when the difference between these voltages is less than a predetermined value. The power supply lead may be the central conductor of a coaxial cable feeding the signal to the repeater and also supplying power to the repeater amplifier. Fig. 6 shows a switching circuit in which power is supplied to the oscillator 5 via lines 3a and 34, the oscillator normally being rendered inoperative by the normally conducting transistor 39. The voltage between the control line 4 and the power line 3b is monitored by the bridge circuit of rectifiers 31. When the voltage difference between lines 4 and 3b exceeds a predetermined value transistor 32 is rendered conductive, 34 and 37 are cut off and 39 is rendered conductive to short circuit the power supply to oscillator 5. When the voltage on line 4 is close to that on line 3b transistor 32 is cut off and via transistors 34 and 37 transistor 39 is cut off to render the oscillator operative to feed a test signal into the communication channel. Power to energize the control circuit 14 is derived from the power supply line by tapping points 15 and 16 to points a little way removed from the supply connections to the repeater, utilizing the voltage drop along the supply line to power the control circuit. Fig. 5 shows a switching system for a two-way communication system using a number of repeaters each including test oscillator and switching circuits 14. Two control lines 4 and 4<SP>1</SP> are used to allow wider tolerances on the switch operating potentials. In this arrangement the system can be tested from either end by connecting the source 17 or 117 to that end and connecting the ammeter 21 or 121 at the other, the meter indicating when testing is proceeding at the other end. Half the repeaters are tested using one control line, the other line being connected to a mid-position voltage which operates no control circuits. Each control circuit is selected by connecting the appropriate control line to the appropriate tapping on the potentiometer, 22 or 122, in use at that time.