GB937776A - Improvements in or relating to bistable magnetic devices and digital data stores including such devices - Google Patents

Abstract

937,776. Circuits employing bi-stable magnetic elements. GENERAL ELECTRIC CO. Ltd. May 10, 1962 [May 10, 1961], No. 17030/61. Class 40 (9). [Also in Group XXXV] Bead-out of the direction of magnetization along the easy axis 5 (Fig. 1) of a magnetic thin film is effected by superimposing on a transverse magnetic field a temporary change thereof in a selected sense (which preferably increases the cross magnetization to a point at which the remanent magnetization vector is turned perpendicular to the easy axis) the leading edge of the pulse produced in a conductor 4 by the consequent temporary change of magnetization along the easy axis producing an indication of the sense of the change (and hence of the information recorded in the film 1) in detector 8. The transverse field may be produced by a current in conductor 3 or by a pair of coils or a permanent magnet, the temporary change in the transverse field being produced by a pulse in conductor 3. Fig. 3 illustrates a data store having a continuous thin magnetic film 11 on a polished aluminium plate 12 and sets of conductors 13, 14, which are respectively parallel and perpendicular to the easy axis, on flexible polyethylene terephthalate webs wrapped round the plate 12. Direct current is passed (if desired only during reading) through selected conductors 13 by triggering selected pairs of transistors 18, 19 (Fig. 4) so that D.C. is then supplied from transistor 20, reading pulses are then superimposed on the D.C. in these conductors, by transistor 21 in response to control pulses applied to primary 22 of transformer 23, to read out a stored word. A word is written into the selected column, if read out is destructive, by applying pulses to conductors 14 (Fig. 3) overlapping the trailing edges of the read pulses applied to conductors 13, the amplitude of the write pulses being insufficient to cause switching of any device in the absence of an overlapping read pulse. Instead of using the leading and trailing edges of the same pulse for reading and writing separate pulses may be used. Specification 919,022 is referred to.