Patent GB-839085-A (GB)
Title: Improvements in magnetic gating circuit
Inventor: BONN THEODORE HERTZ
IPC: G06F7/38
Filed: 1957-04-30
Abstract: 839,085. Magnetic amplifiers. SPERRY RAND CORPORATION. April 30, 1957, No. 13728/57. Class 40 (9). [Also in Group XIX] An electric circuit for performing logical operations comprises cores of rectangular hysteresis loop material having power and signal input windings and a source of regularly recurring power pulses connected to a load by way of all the power windings, the supplying of a power pulse to the load requiring that at least one of the power windings exhibit a low impedance, and the impedance of each of the power windings to a power pulse being determined by the presence or absence of an input signal to the associated signal input winding during the period of time immediately preceding the power pulse. Gating and amplifying circuits.-In one arrangement, Fig. 4, four cores of material with rectangular hysteresis characteristics such as Orthonik or Molypermalloy have power windings 41-44 connected in series between a power source PP of rectangular pulses and a load 46, the cores in the absence of a control signal all operating in the saturation region so that positive power pulses pass to the load. Negative power pulses are suppressed by a rectifier 45, and these pulse periods are utilized by signal sources SS1-SS4 synchronized over 26 to reverse the magnetic state of one or more cores by applying signal pulses to their respective control windings. Each time the signal sources are operative, the positive power pulse immediately following is virtually suppressed since it is wholly absorbed in restoring reversed cores to their original magnetic state. The small magnetizing current effecting the core flux restoration is called a " sneak current " in the Specification, and is isolated from the load in this and other arrangements by a biased rectifier circuit comprising the components 23, 24 and 25. In a modification, Fig. 4A, the sneak currents are eliminated by counter-voltages induced from windings 48a- 48d, a high-value resistor 47 being provided in series with the power pulse source PP to swamp out any current variation due to alterations of the winding impedances. A modification of the Fig. 4 circuit is shown in Fig. 5 in which the signal sources SS-1 to SS-4 are represented by switches, and complementary alternating pulse sources 40, 130 apply positive pulses PP-1, PP-2 in turn to the power and control windings over rectifiers 45 and 51r-54r respectively. When a switch is open the associated core is constantly biased to negative saturation by current from a battery 51, 53, 55, 57, so that no current pulses from PP-1 pass to the load 46, and it is necessary for each battery to have its potential neutralized by pulses PP-2 by simultaneous closure of all the switches for an effective output to be obtained. If the batteries are omitted the arrangement responds in the opposite sense with respect to the switch positions previously described. As the voltseconds required from the PP-1 source to restore cores driven to negative remanence by control signals varies according to the number of cores affected, a separate restoration circuit may be provided for each core comprising a winding 59a-59d and a high resistor 59e-59h ensuring constant current, these circuits being connected to the PP-1 source either in parallel, as shown, or in series. The separate restoration circuits may also be utilized to suppress " sneak currents " as described with reference to Fig. 4A. A series-parallel arrangement is shown in Fig. 6 in which series power windings 61 and 62, together with one of the parallel branches comprising power windings 63, 64 and 65 in series, or 66, must present a low impedance for a current pulse to pass from the PP-1 source 60 to the load L. In a further arrangement, Fig. 7, the application of power pulses PP to a load 74 is inhibited only when signal sources SS-1, SS-2, SS-3 generate pulses simultaneously and so increase the impedance of all the parallel-connected power windings 71, 72, 73 by driving their cores to negative saturation. " Sneak currents " are cancelled by a biased rectifier 75. A modification of Fig. 4 is shown in Fig. 8 in which an output at a load 46 is provided only when all the signal sources SS-1 to SS-4 are inoperative, i.e. the switches are in the open position. The load circuit is energized by pulse source PP-1, and comprises series-connected power windings 41-44 of magnetic amplifiers I-IV the control windings 89a-89d of which are energized by magnetic amplifiers CI-CIV of the complementing type. The latter amplifiers are energized by a pulse source PP-2 which is operative during the intervals between the PP-1 pulses. It follows that when a switch is open, the associated complementing amplifier provides a demagnetizing output to the control winding of a magnetic amplifier I to IV in pulse period PP-2, and the power winding has a high impedance for the duration of the next PP-1 pulse. The signals applied over the switches to control the complementing amplifiers also originate from the PP-1 source. Each complementing amplifier is of the kind shown in Fig. 1, the pulses PP-1 and PP-2 originating from sources 20 and 16 respectively, " sneak currents " being suppressed by a rectifier 25 biased by potential at 23, and the PP-1 pulses being operative over the control winding 21 and the PP-2 pulse source 16. Coupling between the power winding 18 which feeds a load 19, and the control winding, is prevented by a rectifier 22r which is biased in the non-conductive direction by the positive power pulses PP-2 from source 16. An alternative modification of the Fig. 4 circuit is to connect a single complementing magnetic amplifier in series with the load, Fig. 9 (not shown). In a further arrangement, Fig. 11, three cores 110, 111, 112 selectively control the currents in three loads 1-3 in accordance with different combinations of signals from seven signal sources SS-1 to SS-7. As before, two sources of alternating pulses PP-1 and PP-2 having a mutual phase relationship of 180 degrees feed the control and output circuits. Positive pulses from PP-2 are selectively applied by the signal sources to control windings 110d-110#, 111d, 111e, 112d, 112e which are arranged to drive the cores to positive saturation. At the same time negative pulses from PP-1 act in the opposite magnetic sense in reverting windings 110c-112c. The positive pulses from PP-1 are applied to power windings 110a-112a and to windings 110b-112b, both groups of windings acting in the same positive magnetizing sense on the cores. In operation, the windings 110b-112b have the same restoring effect on the core flux as do the windings 59a-59d in Fig. 5, while the pulses applied to power windings 110a-112a act in loads 1-3 according to the winding impedances. The loads are connected as shown so that load 3 only is energized if all three power windings have a low impedance, loads 1, 2 and 3 are energized if winding 112a has a high impedance, loads 1 and 3 become operative if the impedance of winding 111a is high, and so on. The function of the reverting windings, which are energized at the same time as the control windings and act in the opposite sense, is to set the core flux to negative remanence unless this action is inhibited by simultaneous energization of all the control windings on a core. This signal coincidence in a positive PP-2 pulse period is necessary whenever the associated power winding is required to present a low impedance for the duration of the next positive PP-1 pulse. The induction of PP-1 pulses into the control circuits is prevented by a battery 118 which biases the rectifiers 119a- 119g. The Specification also describes a non- complementing magnetic amplifier, i.e. an amplifier the output of which is directly proportional to the input. As shown in Fig. 12, this amplifier comprises a power winding 122 which is connected between a source 120 of positive pulses PP and a negative potential 124. An intermediate (earth) potential is also connected to the power winding through a rectifier 126. In operation, the intermediate potential biases the core to negative saturation so that the positive-driving pulses PP produce no output. If, however, an input pulse 55 of sufficient magnitude is applied to winding 125, the effect of the bias is completely neutralized and the core flux remains at positive remanence. The next PP pulse is then effective in the output circuit due to low impedance of the power winding. A gating circuit comprising several of the arrangements shown in Fig. 4 is described with reference to Fig. 21 (not shown). Half-adder circuits.-As shown in Fig. 15, the binary signals to be added are applied over leads 130, 131 during power pulse periods PP-2 to the control windings 160, 161 of a magnetic gate comprising cores 154, 155 and to a non- complementing amplifier 162. When the PP-2 pulses are quiescent, the amplifier and the gate provide outputs in response to power pulses PP-1 which are respectively applied to a complementing amplifier 135 and a non-complementing amplifier 139. Final outputs on a sum lead 137 and a carry lead 139b are obtained in the pulse periods PP-2. The power windings 156, 157 of the gate normally present a high impedance as both cores are biased to negative saturation by battery and resistor circuits 158, 159, but if both control windings are energized simultaneously the bias is overcome and an effective PP-1 output pulse is obtained. Amplifier 139 then applies a pulse in period PP-2 to both the sum and carry leads 137, 139b. In this arrangement a pulse appears on the sum lead 137 only when inputs on leads 130 and 131 are either present or absent simultaneously, while synchronism between input and output is effected over a circuit 165. An alternative half-adder circuit is shown in Fig. 17 in which the signals to be added are applied at terminals 170a, 170b during the time periods when all the pulse sources R, RR and PP are negative or zero.