Patent GB-418448-A (GB)
Title: Improvements in or relating to telephone systems
IPC: C08L7/00
Filed: 1933-04-24
Abstract: 418,448. Automatic exchange systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, TAYLOR, R., 30, Oulton Road, Wavertree, both in Liverpool, and BAKER, G. T., Blackbrook, Caerphilly, Glamorgan. April 24, 1933, No. 11938. [Class 40 (iv).] Group selectors linked to secondary finders and used for local calls only under overflow conditions are used also for incoming calls from an adjacent exchange by connecting incoming junctions to the banks of the secondary finders. Local call; finder operation under normal conditions. Two primary allotters, Figs. 6, 7, are associated with two groups (A and B) of 100-point finders, each group containing regular (directly-linked) and auxiliary (indirectly-linked) finders of which the latter are normally marked non-selectable over contacts such as rfb4. When a call occurs in either group both allotters are started and each allots a finder in the calling group so that two finders hunt simultaneously, but if calls occur simultaneously in both groups, each allotter deals separately with one of the calls, the arrangements in this respect being similar to those in Specification 416,851. When an A-group subscriber's line relay L, Fig. 2, operates, common relay S completes circuits for start relays ST in both allotters and for relay 1SR in the B-group allotter to cause testing to take place in that allotter over bank 2a and the A-group finders. Relay G interacts with magnet ALM and when a free regular finder (marked by battery over wiper VW and resistance 11, Fig. 5) is found relay LK operates energizing VR, C in the allotter, and H, E in the selected finder. The vertical magnet VM then interacts with relay G until the calling level is reached when VT operates over wipers 3a, VW, releasing C, H, and operating RS, and causing the rotary magnet RM to interact with relay G. When the calling line is reached, relay PA operates over wipers 3a and P, Fig. 3, and causes the re-operation of C and H, and the cut-off relay K operates over earth on wiper 6a and releases the allotter. Finder operation under overflow conditions. When the last regular finder is taken into use, relays RFB, RFZ are no longer short-circuited, and when relay BP operates in series with magnet ALM on the release of the allotter circuit, RFB and RFZ operate rendering the auxiliary finders selectable over wiper VW, terminal S, lead 19 or 20, Fig. 8, and a winding of relay DS, relays OB, FB being operated provided that a secondary finder is available. Relays FB, one in each secondary allotter circuit, also cause relay GG and magnet SDM to interact to preselect an idle secondary finder SF. When another call is originated, the primary allotter operates as before to select an idle auxiliary primary finder and relay DS then operates and energizes DK causing the preselected secondary finder to hunt for the primary finder marked by battery over wipers 7a, 4c, 2b. When this is reached, relay FK operates removing a short-circuit from FR which energizes SK. The operation of SF to energize relays C, H, and release the primary allotter circuit takes place over the secondary finder test circuit and is thus dependent on the secondary finder having completed its operations. If all A-group auxiliary finders become busy, relay OFB, Fig. 7, operates to prevent hunting by the allotter and to operate a meter over lead 22 if another call arrives. If all secondary finders become busy, relay EB operates and prevents the primary allotter from operating. Incoming call from adjacent exchange. The operation of line relay 1L, Fig. 2a, when a call is made over the junction shown, connects ground to leads 14, 20, Figs. 2a, 8, causing the secondary allotters to control secondary finders to search for the calling junction in a manner similar to that described above for a local call under overflow conditions. Specification 376,265 also is referred to.