Patent GB-856014-A (GB)
Title: Improvements in or relating to electric gating devices
IPC: H03K17/82
Filed: 1957-04-08
Abstract: 856,014. Circuits employing bi-stable magnetic elements. PHILIPS ELECTRICAL INDUSTRIES Ltd. April 8, 1957 [April 11, 1956], No. 11381/57. Class 40 (9). [Also in Groups XXXVI and XL (c)] In an electrical gating device comprising a plate of material exhibiting a Hall or Gauss effect, a memory property is obtained by placing the plate in the air-gap of a core of soft magnetic material of considerable remanence, and by providing the core with a control winding, a pulse through which produces a magnetic field capable of maintaining the transmission of a signal via the plate until the field is expunged by a pulse supplied to an erasing winding on the core. As shown, Fig. 1, an annular ferrite core is composed of two sections 1, 1<SP>1</SP>, and a Hall-plate 2 of germanium is arranged completely to occupy an air-gap in the core. To the plate are attached two pairs of electrodes (not shown) the paths between the electrodes of each pair being perpendicular to one another and to the direction of a magnetic field through the plate induced by a pulse supplied to a control winding 5. A signal applied to one pair of electrodes will be transmitted to the second pair of electrodes while the field exists. An aperture 3 divides the core into two equal branches for part of its length, each branch being surrounded by a winding 4 such that an erasing pulse therethrough magnetizes the two branches to saturation in opposite directions. Fig. 4 shows the circuit of a " gyrator " gating device in which a square Hall-plate 2 is disposed in the air-gap of a D-shaped core (not shown), comprising a bar portion and a semi-circular portion on which are wound one or two control windings and an erasing winding. Pairs of electrodes 6, 6<SP>1</SP> and 7, 7<SP>1</SP> on the plate are connected to pairs of terminals 9, 91 and 10, 101 respectively, and each electrode is also connected to the terminal associated with the corresponding electrode of the other pair through a resistor 12 or 12<SP>1</SP>. The direction of transmission of signals through the plate is determined by the direction of the magnetic field, that is, by the polarity of the pulse supplied to the control winding(s). Fig. 7 shows an " and " gating device comprising two three-limbed cores 20, 21, each with a control winding 5 and two erasing windings 4, 4<SP>1</SP>, corresponding erasing windings on both cores being connected in series. One of two Hall plates 2, 22 is located in the airgap of each core and is provided with two pairs of electrodes, the plates being connected in cascade. An input signal to the first plate will be transmitted to the output electrodes of the second plate only when both control windings 5 have received a pulse; similarly, a pulse to both pairs of windings 4 and 4<SP>1</SP> is required to interrupt transmission. An " or " gating device, Fig. 5, comprises a core carrying two control windings 5, 5<SP>1</SP> and two erasing windings 4, 4<SP>1</SP>. In an air-gap in the core is located a plate 13, of material, e.g. bismuth or indiumantimony alloy, exhibiting a Gauss effect, and carrying one pair of electrodes (not shown) by means of which the plate is connected as one resistance arm in a Wheatstone bridge comprising three other resistors and supplied with an energizing current on which is superposed the signal to be transmitted. In the absence of a magnetic field the bridge is balanced, but a pulse supplied to either of the control windings 5, 5<SP>1</SP> induces a field which increases the resistance of the plate 13, producing an unbalance current proportional to the input signal, until the field is erased by a pulse through either of windings 4, 4<SP>1</SP>. As the Gauss effect is greater at low temperatures the device may advantageously be maintained at e.g. the temperature of liquid air. In the embodiments described with reference to Figs. 1, 4 and 5, a second plate such as 2 or 13 in Figs. 1 and 5 may be placed in a second air-gap, the two plates of one device being connected in series. The Fig. 5 and Fig. 7 embodiments can be modified to produce devices having three or more alternative or cumulative transmission requirements.