GB758546A - Improvements in or relating to radio station apparatus - Google Patents

Abstract

758,546. Radio transmitting systems. GENERAL ELECTRIC CO., Ltd., and FAIRNBAIRN, E. P. Feb. 17, 1955 [Feb. 19, 1954], No. 5005/54. Class 40 (5). A radio station comprises a main and a stand-by transmitter 1, 2 and monitoring means 6 for detecting a radio frequency output of the main transmitter to derive a check voltage which, applied to a normally energized relay TA, prevents release of the latter to a second (rest) position, as shown, which would automatically bring the stand-by transmitter into operation. The station may be part of a radiotelephony link, a radio transmission call from a telephone exchange being initiated by earthing, at the exchange, a line ST so that the main transmitter 1 is switched on. Since the relay TA is normally energized by a voltage x the relay TB/2 becomes energized to disconnect the voltage source x from relay TA with a short delay so that, due to the main transmitter output, the relay TA remains energized by the detected R.F. output. But, if the main transmitter 1 has no output, relay TA releases (to its position as shown) so that, relay TB/2 being slower in releasing than relay TA, a further relay TC/4 becomes energized, and is locked by contact tc4. Also contact tc3 so that relay TAR/2 is operated to switch over aerial switch tar1 to the stand-by transmitter. Further, a relay TCA/6 is energized by contact tar2 so that only then is H.T. applied to the stand-by transmitter. The aerial feeder being connected to the stand-by transmitter before H.T. is applied avoids damage to the latter. Speech signals from the exchange over lines L1, L2 are also connected to the stand-by transmitter. A visual indicator and alarm at the stand-by transmitter are also operated by relay TCA/6. Removal of earth potential from ST at the end for call relays TA, TB release as before but relay TCA, TAR and the stand-by transmitter remain operative. Finally, if the stand-by transmitter also fails, a relay TD/4 is energized over contacts ta1, tb1, tc1, and disconnects earth from both the transmitters by opening switch TD4, so that neither transmitter is energized, and a different visual and aural alarm are operated at the relay station. Moreover, warning of failure is given at the exchange because a supervisory lamp dependent on current through lead ST does not glow. When both transmitters are repaired, a reset key 9 is depressed to deenergize relays TD, TAR, TCA. Failure of H.T. supply at the relay station also operates an alarm.