| 摘要 |
786,079. Unattended repeaters. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Feb. 4, 1955 [Feb. 9, 1954], No. 3400/55. Class 40 (4). In a system for the remote supervision of unattended two-way repeaters using an oscillator at each station to transmit to a monitoring terminal during satisfactory operation a signal having a frequency characteristic of that station, and wherein a change of the repeater working conditions is indicated to the monitor by a change of frequency as in Specification 744,346, changes in the tuning circuit of the oscillator 21 are effected by a relay 20 having an energizing winding or windings 28 connected differentially to the anode circuits of the amplifying valves 12, 13; 121, 13<SP>1</SP>. A bias control 41 is connected in one of the anode circuits. The change of condition indicators 89-92 comprise an amplifier 93 having a frequency dependent negative feed-back circuit 98-103 which ensures maximum anode current under normal repeater working conditions. Reflex amplification is provided by rectifier 104 and the tapping on resistor 105 to keep relay 95 normally operated. The nature of a fault indicated by the release of a relay 95 can be determined by reference to the pilot indicators 69, 70, and load indicators 80, 81, as described in Specification 744,346, and by observing the direction of frequency change by rotating the ganged condensers 100-102. Alternative arrangements mentioned include the use of a maximum and a minimum relay instead of contact voltmeter 51, the use of Colpitts or Hartley oscillators and separate monitoring wires. |
