Patent GB-191119573-A (GB)
Title: Improved Circuit Arrangements for Automatic Telephone Systems.
Filed: 1911-09-02
Granted: 1912-06-06
Abstract: 19,573. Siemens & Halske Akt.-Ges. Oct. 12,1910, [Convention date]. Automatic exchange systems.-A relay set, which may be associated with the first selector, repeats the numerically selective impulses over one of the speaking-leads of the selector trunks in series with the test-lead. This ensures a more thorough testing, as it is impossible to build up a connexion over a selector having a defective test-lead. The invention is described in connexion with a twowire system, in which the subscriber's impulsetransmitter causes interruptions of the current flowing in his metallic circuit, there being no earths at the sub-stations. Line-switch VW and master-switch SS, Fig. 1. When subscriber X completes his line circuit by taking down his receiver, the magnet T of the line-switch VW depresses its contacts 6, 7, to engage the leads a<1>, b<1> of the next disengaged first selector GW<1>, the cut-off magnet TR being then energized over contact 8. Relay RS of the masterswitch SS (which is of the sort described in Specification 26,301/06) is energized over contact 9, and moves the switch-arms of all the line switches of the same group till they are above the contacts of the next disengaged first selector. First selector GW<1> and impulse-repeater US, Fig. 1. The impulse relay A of the repeater set US is now energized over the line a, b and inductance Dr, and a slow-release differential relay V over contact 14, winding v<1>, magnet M, contact 9, and magnet Mv. Each current interruption of the series representing the first digit affects relay A and causes the energization, over contacts 20, 17, of an auxiliary relay R, the contact 21 of which supplies impulses to the first-selector vertical magnet H. At the moments when the relay A is de-energized and the relay R energized, the windings v<1>, v<2> of the relay V are both cut off from current, and at the moments when the relay A is energized and relay R de-energized, the windings v<1>, v<2> are both supplied with current, the offnormal contact 26 having been closed at the first step of the selector GW<1>. But the relay V being of slow-release type it holds up as long as the armature of relay A continues vibrating, the currents received by the winding v<1> over contacts 14 and 23 alternately, during the moments represented by the lag of the relay R behind the relay A, being sufficient for this purpose. When, however, the armature of relay A remains steadily against either of its contacts, the relay V has time to fall back. Thus when the series of interruptions is finished, relay V open-circuits at 18 the previously-energized side-switch magnet S, which moves the arms s<1>, s<2>, s<3>, s<4> to second position. The rotary magnet D is now connected in over interrupter U, energizing the magnet S in known manner, and rotates the wipers o', o<2>, o<3> till they reach the unearthed test-contact of an idle second selector GW<11>, whereupon the test-circuit of magnet S over side-switch arm s<4> is broken, and the magnet moves the arms s<1>, s<2>, s<3>, s<4> to third position, cutting out the rotary magnet D, extending the talking connexions to the wires a', b<2>, and connecting the test wiper o<3> to earth. Second selector GW", Fig. 1. The interruptions representing the second digit are repeated by relay A as impulses over contact 20 and lead a<2> to relay A<1>, the return being over the test-lead c<2>, and the vertical magnet H<1> is energized over contact 27. At the first falling-back of relay A, winding v<2> is cut out at contact 25, and relay V becomes energized again, connecting in the side-switch magnet S<1> at 18 and putting the relay R under control of relay A at 17. As described for the first selector, relay V relapses at the end of the series of interruptions and cuts out the magnet S<1>, which moves the side-switch arms s<5>, s<6>, s<7>, s<8>, s<9> to second position. The operation of the rotary magnet D<1> and the movement of the side-switch to third position take place as in the first selector. Connector LW, Fig. 2. Current now flows over the normal contact 28 of the connector, through winding f<1> of a differential relay F, which locks up, and over the test-leads c<3>, c<2>. The interruptions representing the third digit are repeated by relay A as impulses over contact 20 and leads a<2>, a<3> to relay A<2>, the return being over the test-leads c<3>, c', and the vertical magnet H<2> is energized at 30. Relay V, Fig. 1, operating as described in connexion with the first selector, energizes and finally de energizes at 18 a connector relay B<2>, which controls at 31 the sideswitch magnet S<2>, the circuit of which had been prepared at 32 by the relay F. The side switch is thus moved to second position, introducing the rotary magnet D' and energizing the ringing relay L. The interruptions representing the last digit are repeated by relays A, A<2> to the rotary magnet D<2>, and the relay B<2> then relapses as before, transferring the side switch magnet S<2> from contact 31 to 36. Busy signal. If the wanted subscriber is engaged, the magnet S' is kept alive over the earthed testwiper o<9> and a continuous signal is sent back by a buzzer SM over contacts 46, 40 and the lead b<3> to the calling subscriber, who releases by hanging up his receiver. Supply of ringing current. If, however, the wanted line is idle the magnet S<2> de-energizes and moves the side switch to third position, extending the connexions to the wantei line a', b<4>, energizing the line-switch cut-off relay TR<4> over wiper o<9>, and connecting the ringing-relay L to a slowly revolving interrupter UZ. The relay L is of slow-release type, so that a first ringing-current is sent at once over its front contacts and the side-switch arms s<12>, s<13>, and thereafter the ringing is repeated say once every ten seconds. Control signals are simultaneously sent back by buzzer SM over interrupter UZ', contacts 39, 40 and line b<3>. In the first non- ringing interval after the called subscriber replies, a circuit is closed over relay B<2>, contact 41, linewires a<4>, b<4>, contact 42, relay A', and test-lead c<3>, c<2>. Relay A<2> energizes at 30 a winding f<2> which opposes the winding f<1>, so that the relay F relapses, opening its locking contact and cutting out the ringing- relay L. Release at end of conversation. The release of the line-switch VW and first selector GW<1> is controlled by the calling-subscriber, that of the connector LW by the called subscriber, and that of the second selector GW<11> by the two subscribers conjointly. When the subscriber X hangs up, relay A relapses, cutting out-winding v<2>, so that relay V becomes energized again by the current in winding v' and excites relay R, which cuts out the winding v<1> at 14 so that relay V falls back. Before relay R has time to relapse a circuit is closed over contacts 20, 15, 24 through magnets M and Mv. The currents which previously passed through these magnets in series with the winding v<1> and relay RS respectively were not sufficient to energize them, but they now respond and release the line switch and first selector. When the called subscriber hangs up, relay A<2> is de energized and the release magnet M<2> receives current over the offnormal contact 34 and contacts 44, 43. Relay B<2>, in series with relay A<2> in the circuit already traced, at the same time takes earth off the test-lead c<3>, c<2> at 33. The other earth connexion at the sideswitch arm s<4> having alraady been broken, the relay A<1> relapses and energizes the release magnet M<1> of the second selector. Release from defective trunks &c. If for any reason the relay A should fail to respond when the trunk a<1>, b<1> is occupied, the release magnets M, Mv become energized as above and a fresh trunk is seized. The occupation of a selector with defective leads may be notified by a signal.