GB185475A - Improvements in and relating to radiotelegraphy - Google Patents

Abstract

185,475. Ware, P. N. May 23, 1921. Combined transmitting and receiving arrangements; heterodyne receiving systems; thermionic amplifiers and detectors.-Telegraph systems are so arranged that either operator who is at the moment receiving may break in at will on the sending-operator. The receiving-station normally sends out continuous waves which enable the operator at the sending station to hear the signals he is sending out. A break-in is effected by the receiving-operator interrupting his oscillator and (thus rendering the signals audible to the sending-operator. The two stations are practically identical and either may effect the break-in. In one arrangement shown in Fig. 2, signals are transmitted and received on the same aerial 1 which is energized by an oscillating valve 7, the plate circuit of which in. cludes a key 18 and a low-frequency transformer 9 by which beat currents are transferred to amplifiers 10, 12 and telephone 15. The two stations emit normally waves of slightly different frequencies which produce audible beats at both stations. Signals are sent in either direction by keying the local oscillator circuit, the receiver being kept in an oscillating condition by maintaining its key 18 closed. The receiving- operator breaks in by opening his key, thus interrupting the local oscillator and destroying the beats at both stations. In another arrangement, one station of which is shown in Fig. 3, a separate transmitting-aerial S and receiving- aerial 22 are provided at each station, the receiving-aerial being connected to a heterodyne valve 24 the plate circuit of which includes a low-frequency transformer 27 by which beat currents are transferred through an amplifier 28 to the circuit of a telephone P. The sending- key K serves to control two circuits, closure of the key energizing a relay M which first closes contacts X, Y to energize the aerial S. and then closes contacts Y, Z to complete the telephone circuit. When the station shown is receiving, the key K is kept closed, thus enabling received signals to be heard as beats in the phone P. At the same time the emission of waves by the aerial S causes beats in the receiving-apparatus at the sending-station and these beats are heard whenever the phone circuit at the sending-station is closed by depression of the sending-key. The sending-operator thus hears the signals he is sending. If, however, the receiving-operator breaks in by opening his key K, no beats are produced at the sending-station and the sending- operator is informed of the break in. The key K has two arms one of which serves for signalling, and the other for making circuit more or less permanently whilst receiving.