GB579872A - Improvements in electric wave communication systems - Google Patents

Abstract

579,872. Wireless signalling. STANDARD TELEPHONES & CABLES, Ltd. April 19, 1944, No. 7291. Convention date, April 27,1943. [Class 40 (v)] An electric wave communication system comprises a communication set, a control transmitter for transmitting a series of control pulses at instants separated by predetermined time intervals on a carrier wave having. a specified frequency, means at the said set for receiving and detecting the said control pulses, and means responsive to the detected pulses for tuning the said set to each of a plurality of given frequencies in turn in a predetermined order, all of said frequencies being different from the said specified frequency. Fig. 1 shows the arrangement at a transmitter 9 for generating control pulses for varying simultaneously the operating frequency of two intercommunicating transmitterreceivers 10, 11. The control pulses are sent by periodically closing at 19 the cathode circuit of oscillator valve 13 by means of a relay 20 controlled by a number of contacts 22, 23 on a disc 21 rotated by a motor 26. At the end of each series of pulses, a broad contact 23 on disc 21 closes contact 19 for a prolonged period. At the same time a contact 25 on a second disc 24 closes the circuit at 29 of a gas discharge tube 28 operating into a condenser resistance combination 18, 31 to produce a long series of rapid pulses. These pulses are fed through resistance 17 to modulate the grid of oscillator 13 and produce a series of control pulses which bring all the sets 10, 11 back to the datum condition, thus ensuring that they are synchronised. Fig. 3 shows the arrangement at one of the communication sets 40 having a normal aerial 41. A separate receiver 42 is tuned to receive the control pulses which are detected at 42a and, after shaping at 43 ... 46, are applied through condenser 48 to a delay network 50 ... 57, connected as shown to the grids of gas discharge tubes 58 ... 61 controlling relays 68 ... 71. Only tube 58 is connected to the high tension source-thus the first pulse operates tube 58 alone to energize relay 68 to close switch 62 and connect condenser 63 to alter the tuning. Since tube 58 is now ionised, tube 59 is connected to the high-tension and so the next pulse operates tube 59 and hence switches in condenser 65. Similarly the third pulse switches in condenser 67 and the fourth pulse energizes tube 61 to open contacts 72 to disable all the tubes. This cycle is repeated continuously to tune all the sets simultaneously through a series of frequencies. A series of synchronising pulses follows each cycle and owing to delay network 56, 57 operates to fire all the tubes 58 ... 61 at the same time, thus ensuring that all the sets start the cycle at the same stage. The tubes 58 ... 61 may be replaced by electromagnetic relays, Fig. 5 (not shown).