Digital indicator circuitry

856,166. Circuits employing bi-stable magnetic elements. NATIONAL CASH REGISTER CO. Jan. 9, 1958 [Jan. 16, 1957], No. 864/58. Class 40 (9). [Also in Groups XIX and XXXV] A digital computer comprises a magnetic core data processing unit, and a programming unit for controlling the sequence of operations performed in the processing unit, the programming unit being itself controlled by signals derived from the processing unit. General.-The computer described is applied to the positioning of a shaft 21, Fig. 1, of a device 17 indicating a vehicle bearing, a pulse on output line 68 or 69 moving the shaft and indicator pointer one step clockwise and counterclockwise, respectively. The shaft may be mechanically coupled to a synchro-receiver 26 controlling the vehicle steering mechanism. The programming unit 10 (Fig. 6) and data processing unit 12 (Fig. 5) each comprise similar magnetic core registers. The E register, Figs. 1, 3 and 5, receives serially from a matrix memory 11 an 8-digit binary number word representing a desired vehicle bearing, which is compared, at 23, Fig. 1, with the number in the F register representing the present bearing, the comparison result being given by the one-digit A register. If the numbers are unequal, the F-number is adjusted by adding or subtracting " 1's," corresponding pulses being supplied to line 69 or 68. This operation is performed by repetitive cycles of programme-unit-controlled operations (see Group XIX), each lasting for a word period, the " programme count " being given by the combination of binary outputs from registers J, K, L, Fig. 6. Timing pulses.-Generators 38, 40 and 39, Figs. 3 and 5, driven from pulse source 15, e.g. a multivibrator, produce half-drive pulses Cc, Cs and P 1 -P 8 , Fig. 3b, a pair of which of like polarity will drive a core to saturation in one direction or the other. As shown, a core switching cycle comprises 4 periods Rs, Wc, Rc, Ws. Pulses Cc, applied to register control cores, are effected during Wc, Rc for writing into and reading from such cores respectively; pulses Cs, applied to register storage cores, are similarly effective during Rs, Ws; and the digit-select pulses P 1 -P 8 are effective successively each during all 4 periods of a corresponding cycle. Pulses produced by a further generator 16, effective during write periods Wc, Ws, are combined in OR gate 20 and applied to register transfer circuits TC. Magnetic core registers; transfer circuits.- Each of the registers comprises one o