Patent GB-431590-A (GB)
Title: Improvements in electric selector systems
IPC: H04Q1/32
Filed: 1934-03-05
Abstract: 431,590. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, London, and EDWARDS, H. J., 5, Summerhill Road, Dartford, Kent. March 5, 1934, No. 6907. [Class 40 (iv)] [See also Group XXXVIII] A relay for determining the end of an impulse train remains de-energized during the train due to an alternating flux being set up in the core, the flux in either direction being insufficient to operate the relay which, however, pulls up at the end of the train due to the building up of a steady flux of the required magnitude. The relay may have one or two windings. An application to steering trains of impulses to registers is shown in Fig. 1. The A and B relays (represented by contacts only) pull up when the circuit is taken into use, and AC remains unoperated in a balanced bridge. On the first relapse of A, a circuit is made for C(i) and the bridge is unbalanced to operate AC which is quick acting and makes an opposing circuit over C(ii) which is maintained during the train. Rectiner R prevents current flow from b over C(i). The impulse operates register BDM over distributer U. Winding C(i) has more ampere turns than C(ii) the ratio depending partly on the ratio of the break to make periods, and during the impulse, the flux is slightly in the direction due to C (i). When A pulls up again, the circuit of C (i) is broken arid C(ii) builds up a flux in the opposite direction but not sufficient to operate the relay. At the end of the train, a remains open sufficiently long for C to operate over C (ii), step the distributer and hold itself until the magnet UDM has fully operated. Relay C also releases AC so that when UDM has released C, the circuit is ready to receive the next train. Winding C(i) may be in series with BDM as shown in the dotted rectangle. A further application to a switch taking two steps per impulse is shown in Fig. 2. When A and B operate, parallel circuits are made over C(i) and resistance Y for magnet DM in which C does not pull up owing to the shunting effect of Y, but the flux over C(i) builds up to a small value. On the first impulse, DM releases and the switch takes one step, the magnet commencing to re-operate over on 2 as soon as movement starts and being held over C(ii) and 'the even-contact commoning until the impulse ceases. C(i) is opened and the flux in C reverses due to C(ii) but before C can operate A pulls up again and DM takes another step. C(i) energizes again but the shunt Y is now disconnected since C(i) has to oppose a small flux in the opposing direction due to C(ii). At the end of the train, C operates over C(i) and opens the self-stepping circuit of the magnet. In a modification for a switch stepping once per impulse, a battery connected winding of C is connected over off-normal make contacts to the front of the impulsing contact which is grounded, while the other winding of C is connected in series with a break contact of itself, the magnet, and the back of the impulsing contact. An arrangement utilizing only one winding is shown in Fig. 3 in which C is connected between ground and a point S which is connected to positive battery, e.g. booster battery P, over a neon tube T, and to the normal positively grounded battery N over a. In the normal condition of the circuit, T does not strike over P, S, C and the circuit is open between a and S. When A pulls up, the dotted connection between a and S is completted in any convenient way. On the first impulse T strikes over P, S, N and current flows over C and resistance Y but before C can operate, a opens and T continues to glow over rectifier R, and relay C the current in C being in the opposite direction. Relay C is shunted by resistance YB to prevent extinguishment of the tube during reversals of flux in C, and an inductance may be included between P and S as a further safeguard. Prolonged opening of a causes C to pull up over the tube. In all arrangements, C may be slugged to make it slow to operate if impulsing is slow.