Improvements in or relating to radio relaying systems for telephony, television, facsimile and like methods of transmitting intelligence

摘要

610,977. Duplex radio signalling. CINEMATELEVISION, Ltd., MORGAN, M., and GRAHAM, G. E. G. April 18, 1946, No. 11957. [Class 40 (v)] Signals are relayed in either of two directions by switching a receiver and a transmitter between two aerials, either of which can be used for transmitting or receiving. Duplex working is achieved by rapid, synchronized switching. Signals received at aerial 2, Fig. 1, pass via channel A, E, H to a receiver and demodulator 3, modulator 4 and transmitter 5, and to the transmitting aerial 6 via channel C, D, F. The channels are an integral number of half-wavelengths long, the unwanted pair presenting an infinite impedance by being short-circuited at the mid-point by switch elements B, G, e.g. diodes controlled by a trigger circuit 8. Conversely, signals may be received at 6 and transmitted at 2 by closing switches D, F, and opening switch B, G, to use channels F, G, H and C, B, A. When the channels comprise wave-guides, the short-circuiting elements may be gas switches triggered by local oscillating signal generators. In a modification, Figs. 3 and 4 (not shown), interlocked mechanical switches are used to open and close the channels. In a further modification, Figs. 8 and 9, an occulting disc with semi-circular slots 23, 24, opens and closes the channels LM, JK, and OK, LN, in turn as it is rotated by a synchronous electric motor 22.