GB1483806A - Telephone systems - Google Patents

Abstract

1483806 Automatic exchange systems SIEMENS AG 6 Dec 1974 [20 Dec 1973] 52767/74 Heading H4K An arrangement including a counter for counting ringing tone bursts is provided in order to call a number of subscriber stations sequentially. The Figure shows an arrangement for controlling the ringing of two subsets. A counter comprising three bi-stable circuits ZK is provided which counts ringing signal bursts and the counter is coupled to gates G4 and G15 in such a manner that gate G4 receives an enabling signal on wire 6 whilst the counter is counting from 0 to 3 and gate G15 receives an enabling signal from gate G14 whilst the counter counts from 4 to 7, the process repeating for as long as the ringing signal persists to open and close contact 1ar. By means of the gates G4, G15, line switches AK1, AK2 are operated during the respective count ranges of counter ZK to cause calling signals to be supplied during alternate periods, of 4 ringing signal bursts to the pair of subsets. When the call is answered at a subset while it is being called, e.g. subset H, a circuit RS3, enabled during the subset's ringing period via gate G8, is switched by an input on wire 12 to hold the line switch AK1 via gate G4. Simultaneously switch 25 is closed and a binary 0 present on wire AU during the whole ringing operation is charged to 1 to reset the counter ZK. If a subset is busy when the exchange line provides ringing current, a respective switch 2S, 3S is closed to prevent an enabling signal being supplied to the respective one of circuits RS3, RS4. However the calling signal is still supplied to the busy subset. The arrangement can be modified to sequentially ring a greater number of subsets cyclically until one answers. The circuitry may be in monolithic integrated module form.