GB1164954A - Improvements in or relating to Electric Circuit Arrangements for Identifying Marked Feeder Lines in Telecommunications Exchange Systems. - Google Patents

Abstract

1,164,954. Automatic exchange systems. SIEMENS A.G. 10 April, 1968 [12 April, 1967], No. 17165/68. Heading H4K. An electronic line finder comprises a cascade of stages each of which comprises two OR-NOR gates which are so interconnected that if a marking denoting a calling line is present on one of the gates when a stepping potential occurs on the other gate then the output of the latter is inhibited so as to prevent further stepping and an output signal indicative of the stage and hence of the identity of the line associated therewith is given. The finder is of particular use in a code-multiple telegraph exchange. When a large number of subscribers are involved, a separate cascade is provided for each digit position of the line's number. Operation.-The two gates referred to above have the references 1b(-6b) and 1c(-6c) in the hundreds, tens and units cascades. A start potential from central control is applied to terminal F and used to set bi-stable iE provided that none of the units gates 1b-6b is marked (this will be so if a hundreds and tens identification has not taken place). Normally the output from iE then sets iZ so that hunting can take place in the hundreds cascade. If in the latter, gate 2b say, is marked then the hunting potential injected by NOR gate f is stopped by gate 2c and an output signal is provided by 2d. A selector device (not shown) then causes one of the tens stages to be marked and the output from the marked hundreds stage is used inter alia to reset iZ and to start hunting in the tens cascade (via NOR gate e). A process similar to that in the hundreds cascade takes place and finally yet another similar sequence of events occurs in the units cascade. In the latter an output from the marked output gate 1d(-6d) is applied via NOR gate h to central control to denote the end of hunting.