| 摘要 |
473,167. Directive wireless signalling. LORENZ AKT.-GES., C. Dec. 12, 1936, Nos. 34159 and 34160. Convention dates, Dec. 12, 1935 and May 19, 1936. Addition to 447,707. [Class 40 (v)] Relates to circuits of the type described in the parent Specification for counting the number of signals of two different kinds received from a rotating radio beacon. The signals applied to the counting circuit each consist of a positive and negative impulse, the sign of the first impulse of the pair determining which kind of signal is being received, and are applied in push-pull from a transformer T2 to a pair of discharge tubes Rl, R2. The first impulse of the pair triggers one or other of the tubes R1, R2 to discharge the condenser C in the common anode circuit through a counter Z1 or Z2, the second impulse being ineffective owing to the resulting lack of anode voltage on the other tube. As the beacon rotates the signals wane and wax in amplitude, and in accordance with the present invention in order to reduce the liability of the counters being operated by interfering impulses, the grid bias of the tubes R1, R2, is made dependent upon the signal amplitude by an A.V.C. system comprising one of the diodes of a double diode valve D, which rectifies signals supplied from a winding S on the transformer T2 to charge a condenser C4 in the said grid circuit. The condenser C4 is shunted by a rectifier K which prevents the grids of tubes R1, R2 from becoming positive. The other diode of the valve D is used to provide A.V.C. potentials for the high frequency amplifier H. In order to minimize the false operation of the counters Z1, Z2 by interfering impulses during the half-revolution of the transmitter when there would normally be no signals and the tubes R1, R2 would be at their maximum sensitivity, signals are emitted, during this period, of such a form that the differential indicator operated by the counters Z1, Z2 swings about its zero position.
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