| 摘要 |
526,860. Directive wireless signalling. SOC. FRANCAISE RADIOELECTRIQUE. March 27, 1939, No. 9554. Convention date, April 8, 1938. [Class 40 (v)] A low-frequency switching current is applied in phase-quadrature to the deflecting-coils of a cathode ray tube, so that, in the absence of signals, a circular trace 1, Fig. 2, is produced on the screen. The pick-up voltage from a pair of crossed aerials, and a vertical aerial, is then alternately switched in rapid succession to the anode of the indicator tube, the effect being to deform the circle into cardioid traces 2, 3, on both sides of the reversing switch. The line B<SP>1</SP>, B which includes the two " dips " is at right-angles to the direction of the beacon transmitter, whilst the sense is indicated by the point of maximum radius of the brighter cardioid. Instead of using " interlocking " signals, the carrier-wave may be periodically interrupted, in which case only one cardioid is produced and the direction of the beacon will be at right-angles to the line A, A<SP>1</SP> in Fig. 1, towards the maximum of the trace 2. The screen may be masked so as to leave only the area covered by the circle 1, Fig. 2, exposed to view.
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