Ferranti-Packard Limited

Christopher Gordon Helwig

Blanking means operable voluntarily or in the event of power failure are provided for an electromagnetically operated display which comprises groups of rotatably mounted elements having opposed faces of contrasting colors, each element carrying a magnet rotatable therewith, the orientation of each element and the choice of contrasting color displayed thereby being determined by the magnetic field formed by an adjacent reversibly permanently magnetizable field forming member. A winding is provided corresponding to each field forming member located so that a pulse through said winding in a predetermined sense will magnetize said field forming member in a corresponding sense. Write circuit means interconnects the windings in such a group and connects them to a power source, the write circuit means being arranged so that the windings of individual elements may be selectively energized to display a desired pattern for said group. The blanking circuit includes a capacitor and is superimposed upon the write circuit means. The blanking circuit is arranged so that the capacitor may discharge contemporaneously through the windings of the group to produce a predetermined pattern therein and has switching means selectively designed to permit or prevent the discharge and connections allowing the charging of said capacitor.

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Toronto, Canada

Christopher Gordon Helwig