Arrangements for distribution and control circuit to monitor and control connections between two generators and two identical frequency with a multiple of distribution networks

摘要

1443964 Automatic exchange systems PLESSEY CO Ltd 6 Sept 1974 [9 Oct 1973] 47018/73 Heading H4K In an arrangement in which two multifrequency generators each serve a separate group of multi-frequency utilization devices (e.g. senders) to which they are connected by respective distribution networks, the outputs of each generator are monitored and upon failure of any output that generator is disconnected from its distribution network and the other generator connected to supply both networks. As described the invention is used for inter-register signalling using 2 out of 6 multi-frequency senders. Two generators each normally producing all six frequencies simultaneously each normally supply all six frequencies via isolating resistances and transformers to four groups of ten senders. The six outputs of each generator are monitored by corresponding bi-stable detectors providing six inputs to a seven input AND gate which receives its seventh input from a test key. In the event of a detected output failure or a test the AND gate responds enabling a set of relays which immediately disconnect the generator with a defective output and enable a timing circuit. If the fault is due to a distribution network failure the defective output immediately restores, the AND gate responds, one relay of said set releases to prevent connection of the defective distribution network to the other generator, the timing circuit is inhibited and a prompt alarm lamp and the appropriate distribution network defective lamp are illuminated. If however the defective output from the generator persists the timing circuit times out, a relay operates to connect the outputs of the other generator to both distribution networks and a deferred alarm lamp and the appropriate generator defective lamp are illuminated. The attendants console also has keys to allow one or other of the generators to be removed for servicing. These and the previously mentioned pair of test keys are only effective when the system is working normally and the keys of each pair are interlocked on a one only operated basis. A reset key to allow re-introduction into service of repaired equipment is also provided.