Patent GB-780884-A (GB)
Title: Improvements in counting circuits
IPC: H03K3/45
Filed: 1955-04-26
Abstract: 780,884. Electronic counting-apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. April 26, 1955 [May 3, 1954], No. 11993/55. Class 106 (1). [Also in Group XXXIX] A counting circuit comprises a bi-stable trigger pair and a saturable magnetic component which can take up a plurality of stable states of magnetization on being progressively magnetized towards saturation by successive quantised pulses, the direction in which magnetization takes place being reversible by changing the stable state of the trigger pair. The circuit is used to count the quantised pulses in equal groups, each group taking the magnetic component from saturation in one direction to saturation in the other direction, the trigger pair reversing its conducting state on attainment of saturation of the core in either direction. As shown in Fig. 2, the magnetic component is a core 10 having a near rectangular hysteresis characteristic and carrying two windings 11 and 12, each being in circuit with triodes VI and V2 respectively. The resistor chains 18, 19, 20; 21, 22, 23, are such that either V1 or V2 conducts. Suppose V1 conducts, then the added current through resistor 18 ensures that the cathode of diode D1 is at about 60 volts while that of diode D2 is at about 200 volts. To generate quantised pulses, a positive pulse is applied to the grid of a valve V3 and triggers the valve to energize a coil 31 in a pulse transformer 14. A voltage induced in coil 30 holds the grid of a valve V4 positive and causes it to conduct for a time interval determined by the time constant of the LC circuit 15. The time of conduction of V4 determines the length of the quantified pulse which can be adjusted by the variable capacitors in the circuit 15 so that 10 such pulses of 200 volts induced in a coil 32 are required to move the core 10 by equal steps of magnetization from one state of saturation to the other. With valve V1 conducting and a 200-volt pulse applied to coils 11 and 12, magnetizing current will flow in coil 11. Auto-transformer action induces a voltage of 200 volts in coil 12 raising the anode of D2 to 400 volts above earth; conduction through diode D2, however, is attenuated to small proportions by the resistors 22, 23. When the tenth pulse drives the core 10 to saturation the impedance of coil 11 is reduced and the voltage at the cathode of D1 rises to about 200 volts with a corresponding increase in current through resistors 19 and 20 and in parallel through VI. In consequence valve V2 is forced to conduct, passing anode current through resistor 21 which drops the voltage on the grid of valve V1 to cut-off. The next quantified pulse will therefore find a conductive path through coil 12 in series with valve V2 to magnetize the core in an opposite sense. The change-over in voltages of the cathodes of D1 and D2 indicates that ten pulses have been counted and enables the circuit to be connected in cascade to register the units of a multi-digit number. By pulsing the trigger pair to reverse conduction of the valve V1, V2, when the core has a number of pulses stored, subsequent pulses will effect subtraction from the number.