Patent GB-230485-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1925-03-07
Abstract: 230,485. Telephon Apparat Fabrik E. Zwietusch & Co. Ges. Kommanditges. March 7, 1924, [Convention date]. Automatic exchange systems.-Subscribers lines are divided into groups NI, NII, Fig. 1, and calls within the group are made over trunk lines 1 - - 5, 6 - - 10 local to the group. Calls from one group to another are made with the aid of connecting arrangements KR equally available to either group, whereby any trunk of one group can be connected to any trunk of the other by a single switching operation. Fig. 2 shows the lay-out for a system of three groups, each group then having two coupling means KR available to it. The invention can be carried out with wiper switches, but is described in connection with a system in which relays alone are used for responding to impulses and completing the connections. In the system described there are two groups of fifty lines and two impulse recorders LW 1, 2 are provided, common to the whole system. Selection of trunk and impulse recorder. When subscriber 21, Fig. 3, makes a call, and provided neither impulse recorder is at the moment marking a trunk, his line relay L1 pulls up and energizes the nearest idle relay KH1, KH2 &c. particular to the trunks of the group in the vertical row corresponding to his line over the contact sp1. Assuming the first trunk to be idle, relay A1 is energized over the loop and sluggish relay V1 marks the trunk busy by switching over sp1 from the wire 2 to the corresponding wire in the next trunk, and energizes cut-off relay T1 over the holding winding II of relay KH1, and also relay DW1. The latter energizes relay WV1 or WV2 in series with the relay WP in whichever impulserecorder, Fig. 5, is idle. (If both are idle WV1 at once opens the circuit of WV2.) The operated relays WV, WP lock up in a circuit dw12, WV1(II), 26, wp4. Impulse recorder. Relay A1 repeats dialled impulses over wire 27. Relay Q, Fig. 5, is energized at the beginning and falls back at the, end of each digit. The first impulse of the tens digit energizes relay F over back contacts of all the relays ZI - - ZV. Relay F energizes relay ZI which locks up in series with relay ZH. At the end of the impulse, relay F falls back and the second impulse energizes relay ZII which unlocks relay ZI. The sixth impulse energizes relay ZD which locks up, and since relays ZI - - ZV are again all de-energized, the seventh energizes relay F and the chain is built up again from relay ZI. The relapse of relay Q at the end of the digit energizes relay G which locks up and switches the impulse circuits to the relays ET - - EV &c. These are operated in the same way as the relays ZI - - ZV &.c. The second relapse of relay Q, energizes a marking relay N provided that the corresponding relay of the other recorder is not energized. Completion of local call-subscriber 21 to subscriber 22. Marking relay N energizes the relay P<21>/25 which is common to five subscribers over a contact of relay EE, Fig. 5, and the tens counting chain and relay R2, individual to subscriber 22 is then energized if No. 22 is idle over units chain and energizes line relay L2. The relay N also energizes relay S1 which energizes relay SP1, common to the whole group, to prevent momentarily any other testing within the group, and relay ABS1 in series with winding I of relay KH3. Relay ABS1 releases relay DW1 which releases the impulse recorder. The relapse of relay WV1 is followed by that of relays S1, SP1. Relay KH3 locks over its winding II in series with cut-off re. lay T2 which connects relay R2 to the subscriber's (direct current) bell. Subscriber No. 21 gets an audible indication of this, failing which he knows that subscriber No. 22 is busy. When the called party responds, relay R2 is released. Talking current is supplied over relay A1 and the impedances DR. Release. When both parties hang up, relay Al releases relay V1 by which all the operated relays are held. Completion of call to another group-subscriber 21 to subscriber 78. Operation of the marking relay N energizes relay P 76/70, Fig. 4, and relay RG of subscriber No 78 which energizes line relay L6. Relays S1, SP1, Fig. 3, pull up as in the case of a local call. Relay L6 energizes the nearest idle relay KH5 which connects the subscribers line to its trunk and locks up over its winding II in a circuit including cut-off relav T6. relay G5, a contact s13 of relay S1, Fig. 3, relay KR1(I) and relay G1, Fig. 3. Relay T6 cuts off line relay L6 and rings the wanted line. Relay G5 energizes relay V5 which locks up relays T6, KH5, G5, and energizes relay ABS5(II) in parallel with relay G5. Relay KR1 locks up and connects the two trunks together, whereupon relay A5 pulls up over the calling loop and holds up relav V5. Relay G1 releases relay DW1 to release the impulse recorder, busies the trunk 1 - - 4 to the relays such as KR1 and removes a short-circuit from relay ABS1(II) which pulls up in series with relays KH1, T1. Relay G1 also completes a holding circuit for itself over g15, KH1(II), T1. Current in this circuit opposes the original energizing current, but the relay is arranged not to release by mechanical means. When the called party replies, relay R6 is released. Talking current is fed to the two loops over relays A1, A5 and the impedances DR. When both subscribers hang up, these relays release the connection. Call from subscriber 78 to subscriber 21. The call is effected in the manner just described, but relay KR1(I) is energized in the opposite direction to that in the case of a call from subscriber 21 to subscriber 78. Winding II, however, receives current in the same direction in both cases so that the two windings at one stage momentarily oppose one another. The relays KR1 are therefore made mechanically slow acting.