Patent GB-282186-A (GB)
Title: Improved circuit arrangements for hunting switches in automatic and semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1926-10-13
Abstract: 282,186. Siemens Bros. & Co., Ltd., and Patterson, W. G. Oct. 13, 1926. Automatic exchange systems.-In selectors of the kind having two sets of wipers for hunting over two levels simultaneously, and in which the stepping relay G is of the shunt, field type, the windings of, the latter relay are connected to the two test wipers C<1>, C<2> at the end of the stroke of the rotary magnet R, and if both the links to which the wipers are stepped are free, connection is made to the upper link by means of a wiper-choosing relay E, which may be slow-torelease (Fig. 1) or of the shunt field type (Fig. 2). First arrangement, Fig. 1. Sluggish relay E(1) energizes over contact c2 when the selector moves off-normal, and connects up the upper set of wipers. When change-over relay C falls back, the rotary magnet R operates over contact g<1> and connects winding 2 of relay G to test wiper c' over contacts r<1>, e<4>. Winding 1 of relay G is already connected to test wiper C<2>, so that as long as busy links are encountered by both test wipers, relay G continues to interact with magnet R. An impulse, is delivered at g<1> to hold relay E(1) at each energization of relay G. If the upper test wiper C<1> encounters a free link, test Delay H is no longer short-circuited over that wiper and energizes over relay G(2), and completes a holding circuit for itself and relay E(2) over C(2), V, h5, e1. If the lower test wiper c<2> is the first to encounter a free link, relay E(1) falls back and connects up the lower set of wipers, and test relay H, not being short-circuited over wiper C<2>, energizes and locks over C(2), V, h5. Second arrangement, Fig. 2. The rotary magnet R operates over contact g<1>, and connects winding 2 of relay G to test wiper C', winding 2 of relav E being in parallel. Winding 1 of relay G is already connected to test wiper C<2>. and also to ground over winding 1 of relay E. Relay G therefore interacts with magnet R as long as busy links are encountered by both test wipers. If the upper test wiper C<1> encounters a free link, test relay H energizes over relay G(2) and locks over relay C(1). The subsequent relapse of release relay B disconnects relay G(2) from wiper C<2>. If the lower test wiper C<2> is the first to encounter a free link, relay E operates, its high-resistance, winding 1 being no longer short-circuited over that wiper. Winding 1 of relay G, which is in series, is not effective. Relay E locks over winding 2 and connects up the lower set of wipers, causing test relay H to energize. All lines busy. Shaft contacts s<1>, s<2>, s<3> are operated in the last rotary position. Test relay H is disconnected from wiper C<1> and energizes as for a free link. Line relay A is now connected to the calling loop over the line wipers. Busy tone and flash battery are connected alternately to the a-wire, over back and front contacts c<3>, relay (3) being energized intermittently over wire BB. Line relay A falls back during the flash battery period, but release relay B is held at contacts a<1>, c<1>.