Patent GB-704860-A (GB)
Title: Improvements in or relating to electro-magnetic relay circuits
Inventor: ROUTLEDGE CHRISTOPHER ADRIAN
IPC: H03K23/74
Filed: 1950-05-24
Abstract: 704,860. Digital electric calculating-apparatus; statistical apparatus. BRITISH TABULATING MACHINE CO., Ltd. March 21, 1951 [May 24, 1950], No. 13034/50. Class 106 (1). [Also in Group XXXVII A relay circuit for use in an impulse counter comprises an electromagnetic relay, a rectifier in parallel with the winding of the relay, a condenser in series with the winding and a resistance, across which a voltage is applied, connected in parallel with the winding and condenser, the arrangement being such that the relay operates during the discharge of the condenser when the applied voltage ceases. Relay units. Each relay unit described comprises a double-acting relay R1, Fig. 1. When a switch 3 is closed, a condenser 5 is charged through the unoperated relay contacts R1a and a rectifier 6. Insufficient current passes through the pick-up coil P of the relay to actuate it. If the switch 3 is then opened, the condenser 5 discharges through a resistor 4 and the coil P, due to the high back-resistance of the rectifier. and the relay operates. Similarly, if the switch is operated again, a condenser 8 charges through the operated contacts R1a and discharges, when the switch is re-opened, through the unlatching coil L of the relay so that the latter returns to its unoperated state. Adding. Each denomination of a decimal accumulator, Fig. 3, adapted to receive data in the form of timed impulses produced by the sensing of a record-card, comprises four relay units R3- R6 corresponding respectively with the digits 1, 2, 4 and 8, an accept relay R2 and a carry relay R7. The timed impulses are applied to a terminal 12. At the end of a timed pulse, the accept relay R2 is operated. During each following time interval up to and including the "0" time interval, a pulse produced by cam contacts C5 is applied to the relay unit R3 through operated contacts R2a, the number of pulses corresponding with the digit sensed. Immediately prior to "0" time, cam contacts C4 are closed to operate a simple relay R13 so that at "0" time, the accept relay is restored by the pulse produced by the contacts C5, passing over the operated contacts R2a and operated contacts R13a. The pulses applied to the relay unit R3 alternately switch it on and off, every other pulse passing over operated contacts R3a to the relay unit R4. Similarly alternate pulses applied to the unit R4 pass also to the unit R5 and alternate pulses applied to the unit R5 pass to the unit R6. A binary count is thus performed up to a count of nine. The tenth pulse switches the unit R3 off but, due to operated contacts R6a, passes to the unit R6 to switch if off, instead of to the unit R4, and also directly to the pick-up coil of the carry relay R7 which operates immediately. At time "X", following time "O", contacts C3 close to apply a pulse over operated contacts R7a to restore the relay R7 at the end of the pulse and to provide a carry pulse on a lead connected to the contacts R2<SP>1</SP>a of the next higher order. The pulse produced by contacts C3 is of sufficient duration to allow successive carries to take place. In a modification, Fig. 4 (not shown), the four counting relay units are connected so as to correspond respectively with the digits 1, 2, 2 and 4. By suitably modifying the circuits, addition may be performed in other notations, e.g. duodecimal. Subtraction. In the arrangement shown, subtraction is performed by complementary addition under the control of a relay R8. The accept relay R2 is operated at time "9" by a pulse produced by cam-contacts C2 and passed over operated contacts R8a. Pulses are thus applied to the counting relay units R3-R6 at time "8" and successive times until the timed impulse at terminal 12 passes over operated contacts R8b to unlatch the unit R2. The carry unit of the highest order is connected to the input of the lowest order so that, except when the amount registered goes negative, the amount added is the true complement. In the modification, Fig. 4 (not shown), operation of a subtraction relay so alters the connections between the counting relay units that the counting occurs in the reverse direction. When the amount registered goes negative, operation of the highest order carry unit produces a subtractive entry in the lowest order. Subtotal-taking. Control relays R9 and R11 are operated to produce a timed impulse at terminal 13 corresponding with the digit registered. At the end of a cycle, cam-contacts C1 produce a pulse which energizes the accept relay R2. During the following cycle, ten pulses are applied to the counting relays by the contacts C5, and at a time corresponding with the digit registered, a pulse is applied to the contacts R9b. Since these contacts are operated, this pulse does not affect the carry unit R7 but passes over operated contacts R11a to the output terminal 13. In a modification, Fig. 4 (not shown), the complement of the amount registered may be read out by operating the subtraction control relay as well as the read-out relay. Total-taking.-To zeroize the accumulator, a relay R12 is operated, relays R8-R11 being operated through contacts of relay R12. As in subtotal-taking, pulses are applied to the counting relays until a count of ten is reached, when a pulse passes from operated contacts R9b, over operated contacts R11a, R10a and R8b to restore the relay R2 and so prevent the application of further pulses to the counting relays. The amount registered may be read out as a timed pulse at the terminal 13 during this operation. A digit read out from another accumulator, in the form of a timed pulse applied to a terminal 14, may be entered into the accumulator by operating the relay R10. The Provisional Specification refers to Specification 583,973.