Patent GB-653966-A (GB)
Title: Improvements in or relating to the automatic replacement of defectiye repeating or receiving equipment in high frequency electric communication systems
Inventor: TREADWELL CYRIL GORDON
IPC: H04B7/155
Filed: 1948-07-13
Abstract: 653,966. Electric indicating systems. STANDARD TELEPHONES & CABLES, Ltd. July 13, 1948, No. 18795. [Class 40 (i)] [Also in Group XL (c)] In a communication system, in which the normal equipment at a repeater or receiver station is replaced by spare equipment if an abnormal reduction in signal occurs, means are provided to prevent substitution except when the reduction is caused by a defect at the said station. The arrangement is suitable for use in a system having a chain of repeater stations to avoid replacement occurring at stations subsequent to that at which the defect occurs. Fig. 2 shows a repeater station with a receiving aerial 6, normal repeater equipment 8 and transmitting aerial 7. The signals transmitted, which may be of the multiplex pulse type, are received by monitor receiver 10 and passed to a pulse integrating circuit 12 which controls the operation of a relay B. The synchronizing pulses only of the multiplex system are selected by integrating circuit 13 and used to control relay A. The contacts of relays A and B control the operation of relays C and D, so that with normal signals, relays A and B are operated and C and D are normal. When the signals from aerial 7 cease, relays A and B release, and relay D operates, which causes an auxiliary oscillator 16 to be energized to supply signals to the input of the normal repeater equipment. The signals from oscillator 16 are similar to the normal channel pulses but do not include the synchronizing pulse, so that provided there is no defect in the local repeater equipment, relay B again operates. Relay C is of the slow operate type, so that this relay does not have time to operate if relay B operates as above, in response to signals from the auxiliary oscillator. If the fault is in the local equipment however, relay B will remain unoperated and after a delay, relay C operates, the contacts of which disconnect the auxiliary oscillator and replace the normal equipment 8 by the spare equipment 9. A third contact of relay C holds this relay operated until manually released by switch 35 when normal conditions are restored. The operating time of relay C at each station is made slower than that of the relay D, and the operating times of the relays D at different stations along the chain are progressively increased, so that relays C and D do not have time to operate, at stations subsequent to that at which the fault occurs. The substitution of spare equipment at the initial transmitter may be effected by using relays B and C, but relays A and D, and the auxiliary oscillator 16 are not required in this case. At the final receiver, the demodulated output of the combined channels is applied to integrating circuits 12 and 13 the monitor receiver 10 not being required. Means are also provided at the final receiver (Fig. 4), to indicate at which station the fault has occurred, comprising a pointer 41 which is driven by a motor 42 which is energized under the control of relay B. The position of the pointer indicates the delay which occurred before the appropriate auxiliary oscillator operated, and since the stations along the chain have progressively increasing delay times, this may be used to indicate the faulty station. The pointer 41 mechanism has a second pointer 44 associated with the first, which remains at the indicated point, while the pointer 41 is restored to its normal position by a spring when a clutch 43 releases. The clutch 43 releases when relay A operates, and this is an indication that substitution has been effected.