Patent GB-380479-A (GB)
Title: Improvements relating to telephone systems
IPC: H04Q3/00
Filed: 1931-06-13
Abstract: 380,479. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and PATTERSON, W. G., 68, Eltham Road, Lee, both in London. June 13, 1931, No. 17233. [Class 40 (iv).] A signalling arrangement consists in the application of potential to one of a pair of signalling wires to operate a relay, using a common return path which may be earth, a suitable potential being connected by this relay to the other signalling wire to operate a relay, which may be of the polarized or shunt field type, looped across the wires at the original signalling point. The loop relay may disconnect the original signal. An original signal may be sent over either wire by connecting a receiving relay to each wire, and additional signals may be provided for by the use of marginal receiving relays. The signalling wires may be the speaking wires which may be an inter-exchange junction, and the arrangement may be used between two selecting stages in which a selector may be seized over more than one level of a preceding selector or over one level reached by digits of different values, or it may be used to advance a switch to particular position. As described, the invention is applied to a system comprising group selecting stages each controlled by common marking and control circuits, the conversational switches being rotary switches having two sets of doubleended wipers of the kind wiping over two different levels in one revolution. A forward signal over either wire to a seized switch connects up its control circuit so that if the signal is over a particular wire a discriminating relay in the control circuit causes the switch to rotate through 180‹ from normal. The switches are of high-speed type in which the shaft is geared to an armature rotated by a pair of magnets DM1, DM2 energized by a further magnet SM which withdraws a holding sprag from the gearing. The rotating armature has a cam for alternately closing circuits at dm1, dm2 for magnets DM1, DM2 each of which rotates the armature through 90‹. The two arms of a wiper and the corresponding levels are shown in full and dotted lines respectively. The backward signal operating the looped relay at the preceding switch causes the completion of the operating path at that switch. A selector and control circuit tests idle by virtue of battery over wiper DS3 (normal) of the marker, and when a selector is seized, battery or ground is connected, as will appear later, to the b or a wire respectively, in accordance with the digit used to set the preceding selector. Either signal operates K which connects up the control circuit and extends the signalling potential to A(ii) or P. In either case B pulls up, holds K(iii) over H(i) which does not operate, and reverses the battery connection to the incoming wires to switch through at the preceding selector as fully described below. If A was not operated be the signal, it now pulls up. It will now by assumed that the signal was battery on the b wire so that P is not energized. Series relay C energizes and the marker is set, the relapse of C at the end of the train completing the marking circuit over T, DS2 and operating the sprag magnet SM over DS6. Windings K(i), K(ii) have been removed from the impulsing leads by JB which also disconnected the K relays of other selectors associated with the control circuit. Wiper switching relay WS(i) is operated as required over DS4 and is subsequently held over WS(ii). When the selector reaches an idle line in the marked group, battery on the test-terminal operates T which releases SM and energizes TT whereupon battery or ground is connected over DS5 or DS3 to the outgoing b or a wire (according to the digit received) and relay D is looped across the wires. The consequent reversal of potential on the speaking wires at the succeeding switch operates D which cuts out resistance from the circuit of H(i) so that H switches through and holds over H(ii) to ground returned over the c wire which also shunts down T, TT which fall back slowly so that signalling potential is disconnected. Relays,A, B, K, JB, JBB fall back and DS goes home. If the original signal to the selector is ground on the a wire P, PP are operated, and a circuit for the sprag magnet SM is completed independent of wiper DS6. The switch rotates until the second set of wiper ends (dotted) reach normal, whereupon T operates to battery on the normal contact of wiper 10 and the circuit of SM is opened. Relay TT does not operate at this time. Relay PP, which had opened the circuit of wiper switching relay WS to prevent its operation if impulses came in, falls back and re-connects SM to DS6. Remaining operations take place as previously described. Release of selector. H falls back and completes the circuit of SM in which RA also operates to ground the incoming c wire during release. Busy and number unobtainable signals. Battery over BB on last contacts operates T to stop the switch and busy tone is connected to the a wire. If the digit dialled corresponds to a dead group, the terminal in DS6 is connected to SL which connects up NU tone.