GB734721A - Improvements in or relating to testing arrangements in telecommunication systems and apparatus therefor - Google Patents

Abstract

734,721. Testing radio link apparatus. GENERAL ELECTRIC CO., Ltd., and FAIRBAIRN, E. P. May 14, 1954 [May 22, 1953], No. 14476/53. Class 40(5). Test apparatus is incorporated in a radio relay station which upon receipt of a first tone modulation by the " go " receiver disables the "return" 'transmitter,- which is rendered operative again upon receipt of a second tone modulation to retransmit the second tone in the " return direction " via the " go " transmitter, a frequency changer and the " return receiver. A simpler form of the apparatus may be used to enable the far terminal station to be similarly tested. As shown, receipt of the first tone by the " go " direction receiver 7 energizes a relay A through the detector 14. Contact A3 removes the H.T. supply from " return " transmitter 10, A2 closes to prepare a circuit for relay C and A1 closes to connect the second tone detector 15 to the receiver 7. When the second tone is received relay B is energized, and closure of contact B2 completes the circuit of relay C, which locks up over contact C1 and restores H.T. supply to transmitter 10 over contact C1. Transmitter 10 then sends the second tone back - in the " return " direction having received it from " return " receiver 9 which is energized over a loop formed of " go " transmitter 8, and receiving and re-radiating frequency-changer 17 ... 22, the local oscillator 17 of which is energized by contact B1 of relay B. Other relay stations have similar apparatus but are each responsive to an individual value of the second tone frequency, so that a test loop may be formed through one, two, three, &c. relay stations by progressively changing the second tone frequency because although the B relays release in succession the A and C relays remain operated as long as the first tone is maintained. The circuit 17 ... 21 is unnecessary at the far terminal station where the contact B1 is utilized to complete a speech path between the single receiver and transmitter. Information, such as the occurrence of an automatic changeover to stand-by equipment at a repeater station, may be signalled by coding the returned second tone.