GB1129415A - A random access data store - Google Patents

Abstract

1,129,415. Random-access stores. NATIONAL CASH REGISTER CO. 11 July, 1967 [18 Aug., 1966], No. 31757/67. Heading G4M. A magnetic card selected from a magazine is fed past an array of transducing heads 30, a pair of solenoids 56, 58 being selectively energizable to move the array of heads 30 transversely to the data tracks on the card whereby the array of heads co-operates with a selected combination of tracks on the card. The extent of movement effected by solenoid 56 is twice that effected by solenoid 58 owing to the off-centre pivoting of member 50 with shaft 46 carrying assembly 30. Damping of the head-shifting assembly is effected by springs 61, 67 and fluid introduced into chambers 59, 60, a flexible membrane 63 allowing for thermal expansion of the fluid. The store co-operates with a computer which produces binary coded commands designating cards to be selected and tracks on selected cards which are to be operated on. Each track may commence with an identifying label so that, on a first pass of the card past heads 30, correct track selection may be checked. In a'specific example, there may be 144 tracks on a card, and 36 heads in the assembly 30, the track selection command being decoded into a 2-bit signal for controlling solenoids 56, 58, and a 4 x 9 matrix signal for selecting the appropriate one of the 36 heads. A lamp/photo-cell arrangement initiates a read/write operation by way of an AND gate which is enabled when the same head assembly position is in use during successive passes, but which is enabled after a delay, sufficient to allow positioning of the head assembly to take place, when different positions are to be used in successive passes. Preferably the computer is programmed to select successive tracks from the same group as far as possible so that a maximum of four head assembly positions would be required to process an entire card.