Patent GB-768652-A (GB)
Title: Improvements in or relating to resetting apparatus for magnetic cores
Inventor: DREWE JOHN
IPC: H03K23/76
Filed: 1953-08-26
Abstract: 768,652. Electronic counting-apparatus; statistical apparatus. BRITISH TABULATING MACHINE CO., Ltd. June 1, 1954 [Aug. 26, 1953], No. 23569/53. Class 106 (1). [Also in Group XXXIX] In apparatus for automatically resetting to a first saturation state a magnetic core of material with appreciable remanence and a substantially rectangular hysteresis characteristic, consequent upon switching the core to a second saturation state, input pulses for switching the core from the first to the second state are applied to a first winding on the core, and charge a capacitor, in series with the first or a second winding, whose unidirectional discharge through the first or a third winding produces a voltage time integral across this winding sufficient to switch the core back to the first state. The magnetic core gating circuit shown in Fig. 1 translates a digit-representing differentially timed pulse, obtained, e.g. from a record card, into a number of pulses corresponding to the digit value, which pulses may operate a counter as described in Specification 767,005. During each of the " 9 " to " 0 " times of a card-reading cycle, Fig. 2, camcontrolled contacts CB<SP>1</SP>, CB<SP>3</SP>, CB2 are closed in turn. When a card hole is sensed, (represented in Fig. 1 by closure of switch 14) a circuit is completed through contacts CB<SP>1</SP> and R17a which energizes a start winding 2 on a core 7 having a substantially rectangular hysteresis characteristic, so as to switch the core from a " P " saturation condition to the opposite " Q " condition. Upon the next closure of contacts CB<SP>2</SP> a pulse is. applied to winding 3 which switches the core back to P, thus inducing current in storage winding 4 in a sense to charge a capacitor 12 through rectifier 11. During the following card index point, the capacitor is discharged through a circuit comprising rectifier 16, contacts CB<SP>3</SP> and reset winding 5, thus resetting the core to condition Q and inducing an output pulse in winding 6 in a sense permitted by rectifier 13. The process is repeated for each successive closure of contacts CB<SP>2</SP>, CB<SP>3</SP>, thus providing a number of output pulses corresponding to the time of closure of switch 14. At the end of the cycle, the capacitor is discharged through a circuit comprising contacts CB<SP>5</SP> and R17b. If relay contacts R17a, R 17 are switched over, contacts CB4 apply a start pulse to winding 2 at the beginning of the cycle and the sensing of a card hole produces the " stop " pulse, in place of CB<SP>5</SP>, so that a number of output pulses representing the complementary value is obtained. Unwanted output pulses, such as might be caused by a pulse in winding 2, are eliminated by a circuit breaker in the output circuit. In a simplified core circuit (Fig. 4, not shown), a single winding receives both capacitorcharging input pulses and pulses due to the subsequent discharge of the capacitor. Fig. 5 shows a counting circuit comprising a magnetic core 36 arranged to pass from one saturation condition to the other in ten steps in response to pulses applied to winding 35. These pulses may be obtained from a gating circuit as described above or from a transformer as described in Specification 767,005, as shown, pulses from transformer 32 are applied to 35 through resistor 39, contacts 37 and rectifier 38. The voltage across resistor 39 charges capacitor 40 through rectifier 41. Contacts 44 are closed immediately after 37 open, and connect the capacitor through rectifier 42 and reset winding 43 to the junction of resistors 45, 46 which so biases the rectifier that its cathode is normally more positive than the voltage to which the capacitor is charged. When, however, core 36 is driven to saturation, the impedance of winding 35 drops and capacitor 40 is charged sufficiently to provide subsequently a discharge current through 43 which switches back the core to its first saturation state. An equivalent circuit for that of Fig. 5 is discussed, and it is stated that windings 35, 43 should have the same number of turns. In a modified counting circuit, the bias voltage for rectifier 42 is obtained from an additional winding on transformer 32. Reference is made to the use of thermionic valves or thyratrons as switches.