| 摘要 |
502,407. Valve generating circuits; electric control systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., and ROSEBY, P. N. Aug. 16, 1937, No. 22500. [Class 40 (v)] [Also in Group XXXVIII] A high-frequency generator for signalling over supply mains comprises a pair of generating valves V1, V2 connected in a push-pull oscillatory circuit and a plurality of pairs of amplifying valves connected in parallel each pair being connected in push-pull, any tendency in the amplifying valves to self oscillation being overcome by small chokes CH in the anode circuits. In the arrangement shown, the high-frequency current is fed to a hightension network XYZ over the transformer MT coupling it to a low-tension network 1, 2, 3, N, the circuit of the secondary winding of the output transformer OT of the amplifier being connected to balanced windings of transformer MT and containing a condenser C3 to prevent the passage of the supply frequency. All the valves are of the screen-grid type and are fed with operating potentials from the low-tension network. The high-frequency currents may be amplified, or relayed at the same or a different frequency, at the receiving station, and if the frequency is the same means are provided for preventing the amplifier or auxiliary oscillator from becoming self-sustaining. Specifications 435,564 and 490,936, [both in Group XXXVIII], are referred to.
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