GB1101183A - Improvements in magnetic data storage devices reading and head therefor - Google Patents

Abstract

1,101,183. Magnetic recording and playback; digital data storage. MOLINS ORGANISATION Ltd., and D. W. B. MUIR. 29 July, 1964 [2 Aug., 1963], No. 30768/63. Headings G4C and G5R. In a binary data-storage unit wherein discrete storage elements, e.g. magnetic pins 10 spaced around the periphery of an insulating disc 1, Fig. 2, are selectively magnetized in one sense or the other, the read-head 9 comprises a core 12 having a gap which is substantially closed when a pin 10 is disposed therein. A battery 14 passes a biasing current through the read-head winding 16 which preferably just saturates the core 12 when a pin is absent from the core gap. A binary " 0 " magnetizes a pin in the sense such that when read the flux through the readhead core 12 is slightly increased, but as the core is already saturated this has substantially no effect. When a binary " 1 " is read, however, the oppositely magnetized pin causes the core magnetization to drop below saturation thus markedly increasing the inductance of the winding 16. At this value of the inductance, the tuned circuit, formed by a capacitor 18 and the winding 16, resonates with the output of a generator 20 so that the A.C. voltage appearing across the winding 16 rises to a much higher value and is fed over the output lines 21 as the read out signal. Alternatively, the D.C. bias may be such that the core flux is substantially one half that required for saturation when no pin is present in the core gap, the tuned circuit 16, 18, under these conditions, resonating with the generator output. When a pin 10 magnetized in the same sense as the biasing flux is read, the core saturates and the A.C. output voltage across the winding 16 drops as the tuned circuit goes out of resonance, but when an oppositely magnetized pin is read, there is some cancellation of the biasing flux, but the pin remains in resonance. The write-head 8 is similar in construction to the read-head, the write-head winding 13 being energized in one sense or the other over appropriate circuitry 15. The read-head may be " followed " by an erase head which " switches " all pins 10 to the binary " 0 " condition. A combined read-write head may be used. Groups of discs may be mounted on a common shaft for the storage of multi-digit numbers.