GB575462A - Improvements in radio communication systems - Google Patents

Abstract

575,462. Wireless receiving systems. STANDARD TELEPHONES & CABLES, Ltd., and SEATH, E. G. March 17, 1944, No. 5049. [Class 40 (v)] A combination of a wireless transmitter for telegraphy and a receiver for signals of different type, such as speech, characterised in that one aerial is used for both and switching means provided whereby the act of keying the transmitter automatically transfers the aerial from the receiver to the transmitter and vice versa. It is provided that the radio-frequency voltage on the aerial shall be zero before it is connected to the receiver, and conversely, that on changing over to transmit no radio-frequency energy shall appear at the aerial terminal of the transmitter until the aerial is connected to it. In the Figure, when the key 5 is open, the aerial 1 is connected to the receiver 2 by way of contacts 8, 10 of relay 7, which is unenergized ; at the same time, the grids of the R.F. oscillator V1 and amplifier V2 of the transmitter 3 are over-biassed from the battery 4. On closing the key 5, the grid of valve V1 is grounded and oscillation commences ; also the grid of valve V2 is biassed suitably for amplification, since current flows in the circuit comprising the key 5, battery 4, resistances R1, R2 and relay 6, which causes a voltage drop to occur in the resistance R1. Current in the relay 6 causes contacts 11 to close and the aerial relay 7 to be energized, whereby connection 8, 9 is made and the aerial transferred to the transmitter. Relay 7 may be of the kind described in Specification 562,342, [Group XXXVII]. On opening the key 5, bias is applied to valves V1, V2 before the relays 6, 7 transfer the aerial to the receiver. It is arranged that the output circuit of the transmitter 3 shall be out of resonance until the aerial 1 is connected to it, and an additional contact 12 on relay 6 may be used to shut down the receiver when transmitting.