Patent GB-343584-A (GB)
Title: Improvements relating to rotary switches of the kind used in automatic telephone systems
IPC: H04Q3/00
Filed: 1929-11-23
Abstract: 343,584. Automatic exchange systems and switches. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and CHRISTIAN, D. A., Morven, Charlton Road, Charlton, both in London. Nov. 23, 1929, No. 35936. [Class 40 (iv).] The wipers of a rotary switch can extend any one of a number of inlets to any one of the bank terminals with which the wipers connect. The invention is described as applied to a rotary switch with triple-armed wipers which connect with a 120 terminal bank. Three inlets are provided each of which is associated either with each arm of the wiper in turn or with a single arm when that arm is in contact with the multiple bank. Alternatively three single-armed wipers may be provided insulated from each other, mounted with their arms at 120 and arranged to wipe in turn over the same bank terminals. The Provisional Specification states that the three wipers may bridge the bank terminals with different feed rings mounted in the multiple bank. The feed brushes may be mounted in the bank mounting. Systems are described in which the switch is used as a call finder, a forward hunting switch and as the speech path switch in a bye-path system. The call finder and forward hunting switches have their wiper inlets permanently connected. Construction of switches. The wiper arms 1, 2, 3 shown in Fig. 3 are electrically connected with the conductor 7 but insulated from the remainder of the hub on which the feed brushes 9, 10, 11 bear. The feed brushes are so mounted that one of the brushes makes contact with the strip 7 whilst one wiper arm is in contact with the bank, the other two brushes bearing on the insulated portion of the hub. As that arm leaves the bank and another arm enters, the first feed brush leaves the segment 7 and another makes contact therewith. The third brush bears on the portion 7 whilst the third arm is in contact with the multiple bank. As shown in Fig. 5 the three feed brushes 9, 10, 11 are mounted together in the multiple bank and are separated from the wiper by a thin insulating washer 6. Projections 7 on the wiper pass through holes in the washer 6 and the tips of the feed brushes make contact in turn with these projections the projections being so spaced that in a complete revolution of the wiper each of the brushes is connected with each of the bank terminals. Alternatively the brushes may bear on the wiper hub, the hub being cut away in the spaces between the projections 7. Call finder system, Fig. 7. When a call is initiated relay L operates completing a circuit for the relay S in the assignor AS. If the forward hunting switch MS marked by AS is busy, or if the call finder is engaged over another of its outlets such as MS1, relay AK is shorted over either W1 or W2 and DM steps the switch until a free circuit is encountered whereupon AK energizes breaking the circuit of DM and allowing the magnet DFM of the selected call finder to step the finder in search of the calling line. When the calling circuit is encountered with the wiper connecting to the selected forward hunting switch, relay DA energizes over its winding (i) from earth at ak4. Relay DA connects its holding winding (ii) to the circuit, shorts its winding (i) to allow K to energize and breaks the circuit of DFM. Relay DB energizes switching the circuit through to the forward hunting switch MS which operates in the usual way. When K energized L fell away releasing the assignor and when DA pulled up X in the assignor energized releasing AK and allowing the assignor is step in search of another free outlet. On release of the connection MS returns to a normal position but CF remains in the position in which it was last used. When all outlets from MS are busy the wire gp is earthed to prevent assignment of the outlet by AS. A system in which the call finders are of ordinary type and the forward hunting switches are constructed according to the invention is also described. Byepath system, Fig. 10. When the link circuit LK, with its associated byepath switch BPS, is seized, T energizes followed by X, and A pulls up over the b wire. The impulse train is repeated by A to the vertical magnet VM which steps wipers W to the required level and when impulsing has finished the rotary magnet RM steps the wipers W in search of a free switch SC associated with a free outlet in the required direction. The three outlets from the wipers of SC lead in directions corresponding to different levels of the switch BPS. When a free outlet is selected TD energizes stopping hunting, marking the outlet busy in the bank wiped by W4 and switching the b wire through over W2 to the next switching stage. Magnet DM steps the switch SC in search of the link LK and when this circuit is encountered by the wiper of SC connected with the selected outlet, TF energizes from earth over W3 and locks over its second winding, stopping hunting and switching the circuit through. TF on operating shorts its winding (I) allowing KL to energize to release T and the byepath circuit.