Patent GB-192712-A (GB)
Abstract: 192,712. Janson, G. H. Feb. 4, 1922, [Convention date]. Automatic exchange systems.- In systems in which incoming lines IL, Fig. 2, have access to outgoing lines UL, the latter are divided into groups UG1 UG2, UG3, each having independent means, such as a searcher LS1, for selecting the disengaged line to be taken into use. Each searcher searches only in its particular group of outgoing lines, but all the searchers are accessible to all the incoming lines. The incoming lines may be extended to the outgoing lines by call finders, relays, or cross-bar switching- rangements, the latter being described in detail. Similar arrangements may be used at a groupselecting stage. General arrangement. The incoming lines IL may also be divided into groups IG1, IG2, IG3, each line having a group searcher GS, comprising relays R1 R2, R3 for selecting a group, UG1 say, of outgoing lines or a disengaged line searcher, LS1 say. The several groups of incoming lines may select the groups of outgoing lines, or the line searchers, in a different order of sequence, as indicated in Fig. 2. In the arrangement shown in Fig. 3, the incoming lines are divided into groups, IG1, IG2, IG3, each group having a common group searcher GS1 connected to the calling line by relays R. The relays R are so arranged that in the case of simultaneous calls in a group IG1 only one line is connected to the group searcher. The connecting apparatus AK, Fig. 2, and the line searcher LS individual to each group of outgoing lines may form different switching units, which are independent of each other but accessible in common to all incoming lines. In order to prevent double connections in the case of simultaneous calls, a calling line is marked as such only in the connecting apparatus associated with the group of outgoing trunks selected by the group searcher. Confusion when two or more calls occur simultaneously in the same group of lines is prevented by a call sequence controller whereby only the line which obtains connection with the group searcher is marked as calling. When call finders are used and several are started simultaneously, the line searchers LS are dispensed with. Circuit connections. In the system shown in Figs. 6, 7, and 8, only one incoming line IL1. Fig. 6, and one outgoing line UL1. Fig. 8. are fully shown. The line IL1 is represented by its line relay LR1 and cut-off relay UR, other lines in the same subgroup G1 being indicated by their line relays LR2, LR3, and in other groups by the contacts of these relays. The outgoing trunk UL1 is multipled to all the terminals of the cross-bar selector AK<1>, represented bv the contacts KG and magnets AR1, AR2. AR3 and MR1, MR2, MR3. The line searcher LS1, Fig. 8, and the group searcher GS1. Fig. 7, consist of groups of relays. when a call occurs on the line IL1, its line relay LR1 closes a circuit 2 for a primary relay PR1, which locks up in series with a common relay BR, which opens the energizing circuit of all the primary relays PR1, PR2, &c. Relay PR1 also energizes over circuit 4 a secondary relay SR1, which locks up in series with a common relay CR which opens the energizing circuits of all the secondary relays SR1, SR2, &c. Thus only one primary relay and one secondary relay can be energized at a time, thereby preventing confusion in simultaneous calls. The primary and secondary relays earth one of the marking wires MS1 and one of the marking wires MS2, which are subsequently connected to the cross-bar selectors. The relay CR closes a circuit 5 for the group searcher GS1, Fig. 7, which circuit, if the first line searcher LS1., Fig. 8, is free, includes relays GSE1 and PAR3. Relays GSR1, PAR3 lock up in series with relays DR, ER respectively, thereby marking the group searcher GS1 and the line searcher LS1 busy. Relay GSR1 also closes a circuit 6 for a relay MER1, which extends the marking wires MS1, MS2 to the switching unit KA1 associated with the line searcher LS1. Relay ER, Fig. 7, closes a circuit 7, which, if the first outgoing line UL1 is free, includes relay LSR1, which locks up in series with a common relay FR and also energizes a relay GIR1 which connects the marking wires to the cross-bar magnets MR1, MR2, MR3 and AR1, AR2, AR3 of the unit AK1 individual to the outgoing line DL1. Circuits 9, 10 are thus closed to energize the particular combination of magnets MR, AR corresponding to the calling line, thereby closing contacts KG11 to ccnnect the lines IL1, UL1. Relays RR1, RR2 individual to line UL1 are energized over the calling line and cause relay TR to close a circuit 11 over the holding winding HL of magnet AR1, and the cutoff relay UR of the calling line. The line relay LR1 is disconnected, circuits 3 - - 10 being opened successively.