Demagnetizing circuit

Claim 2

A circuit for demagnetizing magnetic objects having remanent magnetic states comprising: a coil to which the magnetic object may be placed in close proximity; a radiant energy controlled resistance in series with the coil; means for connecting the radiant energy sensitive resistance and coil in series with an alternating current source; a radiant energy emission device in close proximity to the radiant energy controlled resistance; and means for energizing the radiant energy emission device to produce a decreasing alternating current in the coil to demagnetize the magnetic object.

Claim 3

A demagnetizing circuit as defined in claim 1, wherein the radiant energy controlled resistance is sensitive to radiation in the visual light range and the radiant energy emission device is a lamp and a light-tight enclosure contains both the radiant energy controlled resistance and the radiant energy emission device.

Claim 4

A demagnetizing circuit as defined in claim 1, wherein the energizing means includes a resistor and a capacitor and the discharge time of the capacitor through the resistor controls the excitation of the radiant energy emission device.

Claim 5

A circuit for demagnetizing magnetic objects comprising: a coil to which a magnetic object may be closely placed; means for connecting the coil to a source of alternating current; a radiant energy controlled resistance in series with the coil, said resistance being responsive to radiation in the infrared and visual light spectrum; a lamp; an enclosure impervious to infrared and visual radiation for containing the radiant energy controlled resistance and lamp; means for connecting the lamp to an energy source; a semiconductor device having its power electrodes connected in series with the energy source and the lamp; a capacitor connected to the control electrode of the semiconductor device; and a resistor connected to the capacitor to discharge the capacitor such that the semiconductor device becomes slowly nonconductive to cause the demagnetizing of the magnetic object.

Claim 6

A circuit for demagnetizing magnetic objects comprising: a coil to which a magnetic object may be closely placed; means for connecting the coil to a source of alternating current; a radiant energy controlled resistance in series with the coil, said resistance being responsive to radiation in the infrared and visual light spectrum; a lamp; an enclosure impervious to infrared and visual radiation for containing the radiant energy controlled resistance and lamp; means for connecting the lamp to an energy source; a semiconductor device having its power electrodes connected in series with the energy source and the lamp; a capacitor connected to the control electrode of the semiconductor device; and a resistor connected to the capacitor to discharge the capacitor such that the semiconductor device becomes slowly nonconductive to cause the demagnetizing of the magnetic object.

Claim 7

A circuit for selectively storing bits of information on a magnetizable sheet-like material comprising: a plurality of magnetic heads each having a coil arranged to extend across the magnetizable material; means for connecting the coils of the heads in series with a source of alternating current; means for connecting a diode in series with the heads during the first portion of a cycle of operation such that direct current passeS through the coils of the heads to magnetize the material adjacent to each head; means for selectively shunting certain of the magnetic heads; a radiant energy controlled resistance in series with the alternating current source; and means for producing a slowly decreasing quantity of energy to impinge on the radiant energy controlled resistance to slowly demagnetize selected areas adjacent to the magnetic heads.

Claim 8

A circuit for selectively storing bits of information on a magnetizable sheet-like material comprising: a plurality of magnetic heads each having a coil arranged to extend across the magnetizable material; means for connecting the coils of the heads in series with a source of alternating current; means for connecting a diode in series with the heads during the first portion of a cycle of operation such that direct current passeS through the coils of the heads to magnetize the material adjacent to each head; means for selectively shunting certain of the magnetic heads; a radiant energy controlled resistance in series with the alternating current source; and means for producing a slowly decreasing quantity of energy to impinge on the radiant energy controlled resistance to slowly demagnetize selected areas adjacent to the magnetic heads.

Claim 9

A circuit as defined in claim 5, wherein the means for producing a slowly decreasing quantity of energy includes a lamp, a capacitor and resistor and the discharge time of the capacitor through the resistor controls the excitation of the lamp.