GB1435368A - Data storage apparatus - Google Patents

Abstract

1435368 Data storage; recording and playback INTERNATIONAL BUSINESS MACHINES CORP 25 Sept 1973 44816/73 Headings G4C and G5R A storage surface 3 (Fig. 1) includes a region 8, 9 for storing data information sensed by data heads 1, 2 and a region 10, 11 for storing servo information sensed by a servo head 4, moved with the heads 1, 2, the servo information in an area 10 sensed when data information is being sensed being different from the servo information in guard band region 11 sensed when the heads 1, 2 are not over data information, logic circuitry 36, 42 (Fig. 6) detecting when the head 4 moves from area 10 to area 11 to prevent recording or reading by the heads 1, 2. As described the storage service is a magnetic disc in which information is represented by the direction of magnetization, adjacent tracks 27, 28 (Fig. 4) in the region 11 each having simultaneously occurring clocking transitions and further transitions a third or two thirds of the way between clocking transitions. In the region 10 some of the clocking transitions (and consequently further transitions) are omitted (see 25, 26) to indicate the start of a track and sectors within a track. When a servo head is positioned over the boundary between two tracks the data heads are over tracks. Logic circuit 36 detects when the servo head is between tracks 26 and 27 to render transistor 43 non-conductive and so maintain capacitor 44 charged to deliver a high signal on lead 48 to inhibit reading/writing. The changing level of this signal is also used to perform head recalibration. Landing regions 22, 23, 24 are provided for when the heads are not in use. The apparatus may also be used to access a stack of discs. The storage medium may be a magnetic drum where data may be stored in magneto optic or electrostatic waves.