Patent GB-914348-A (GB)
Title: Shift register
IPC: G11C19/04
Filed: 1959-10-27
Abstract: 914,348. Stepping registers. INTERNATIONAL BUSINESS MACHINES CORPORATION. Oct. 27, 1959 [Oct. 27, 1958], No. 36423/59. Class 40 (9). A stepping register has storage cores S1 S2, &c., and intermediate cores K1, K2, &c., each storage core being linked to the preceding and succeeding intermediate cores by a circuit including a series capacitor. As shown in Fig. 2, shift pulses from sources A and B in antiphase, as shown in Fig. 5, drive alternate pairs of cores K1, S1 ; K2, S2; &c., or K2, S1; K3, S2 ; &c., depending on switch 34 which determines whether the register steps left or right. A reset pulse source R drives the cores K1, K2, &c. Current entering a winding at the dot terminal tends to switch a core to " 0." For the switch position shown, and with all cores at " 0 " except S1 which is at " 1," an A drive pulse switches S1 to " 0 " producing a clockwise current in windings 10, 12, and 14, which cannot disturb core K1 as it is subject to the A pulse, but switches K2 to " 1." Shift of flux in K2 produces an anticlockwise current in windings 16, 18 and 20 while charging capacitor C2. As the current in this loop starts to decrease capacitor C2 discharges and this discharge is accelerated by an R pulse which restores core K2 to " 0," the consequent clockwise current in winding 20 switching core S2 to " 1."  Clockwise current in the windings 10, 12, 14 as K2 is set to " 0 " is opposed by capacitor C1 which was charged when S1 was switched. When C1 discharges it provides an anti-clockwise current which does not affect cores S1 K1, or K2, as they already occupy " 0 " states. An A pulse, therefor, steps " 1 " from S1 to S2. A subsequent B pulse will similarly step the " 1 " in S2 to S3, and so forth. By throwing switch 34, reversely connected drive windings are used to step the register backwards in the same fashion, it being necessary for the windings 12 and 14, 16 and 18, &c., to have equal turns. The reset source R is dispensed with in the register shown in Fig. 6 where, for the step right connection of the sources A and B capacitor C1 is charged by clockwise current in windings 10, 12, 14, when S1 is switched to " 0 " by an A pulse and C2 is charged by anti-clockwise current in windings 16, 18, 20, as core K2 is switched to " 1." Due to loss over core K2 capacitor C2 is charged less than C1 so that when both capacitors discharge at the end of the A pulse current from C1 has a predominant effect on core K2 and switches it back to " 0." The discharge of capacitor C2 switches core S2 to " 1 " but does not switch core K3 as discharge takes place before the end of the A pulse which holds K3 at " 0." The " 1 " in core S1 is therefore stepped to S2 by an A pulse; a B pulse will similarly step the " 1 " in S2 to S3, and so forth. As shown in Fig. 7, a forward stepping register is constructed to avoid separate drive windings, drive being applied to the windings 12, 14, 22, 24, and 16, 18, 28, 60, &c., from drive sources A and B respectively. Supposing that core S1 occupies the only " 1 " state an A pulse switches S1 to " 0 " and charges capacitor C1 with a current which switches core K2 to " 1." When K2 switches, current flows in windings 16, 18, 20 to charge C2. When S1 is fully switched, winding 10 has low impedance and capacitor C1 discharges, switching K2 back to "0." Capacitor C2 also discharges to switch S2 to " 1 " and also tends to hold K2 in the " 1 "  state, but as there is loss in charging C2 over K2, C1 predominates. Core K3 is unaffected by discharge of C2 as it is subject to the A pulse. A B pulse similarly shifts the " 1 " from S2 to S3. Specification 814,619 is referred to.