GB1016979A - Improvements relating to apparatus for controlling a printer - Google Patents

Abstract

1,016,979. Electric selective signalling. INTERNATIONAL BUSINESS MACHINES CORPORATION. Sept. 7, 1964 [Sept. 30, 1963], No. 36629/64. Heading G4H. In printer control apparatus, representations of characters to be printed are read cyclically from a first store and compared with representations of characters mounted on a movable type carrier read from a second store in synchronism with the respective type characters appearing in the printing position, printing being performed on a positive comparison being obtained. In the particular embodiment, a line of 128 characters is printed using a constantly moving type chain bearing 256 characters, and 128 hammers. As the chain moves by one type element, 8-bit representations of the 128 characters to be printed are read in turn from a first core store and compared with corresponding ones of 128 8-bit representations of the type character in position read from a second store. The comparator output is passed to 128 hammer selection gates enabled in turn by a matrix controlled by the addressing circuits of the first store. The second store may be a core store or a replaceable fixed store. After these 128 read-outs, the addressing circuitry of the stores is advanced by one by a pulse from a magnetic clock-pulse track driven in synchronism with the type chain. After printing of one line, a single mark on a second magnetic track driven with the type chain produces a line synchronization pulse to ensure that store read-out for the next line starts at the correct time. In a modification, a 6-bit code group is stored in the first store for each character to be printed, and a sequence of characters is preceded by one of four 6-bit code groups to identify the character variety (e.g. whether arabic or latin letters or &c.). This latter group is recognized to provide an extra 2-bit control signal for the comparator (no details).