GB1490561A - Bidirectional dual head printer - Google Patents

Abstract

1490561 Control of printers CENTRONICS DATA COMPUTER CORP 29 Oct 1974 [12 Nov 1973] 46650/74 Heading G4H A dot matrix printer comprising two print heads for simultaneously printing respective halves of a line of print, successive lines being printed in alternate directions, is controlled by the following sequence of operations: (a) loading binary signal groups representing characters into a recirculating register, (b) shifting the groups until the one representing the first character to be printed by the right hand print head is shifted into the output stage of the register, (c) temporarily storing that group, (d) shifting again until the group representing the first character to be printed by the left hand print head is in the output stage, (e) converting the stored group into dot matrix form and storing the converted signal, (f) converting the group in the output stage into dot matrix form, and (g) simultaneously applying the dot signals for both characters to their respective print heads for printing. Each pair of dot matrix characters is transmitted column by column, corresponding columns of the two characters being printed simultaneously. The above process is then repeated for the next character for each print head and so on for the whole line, at the end of which a new line of characters is stored in the recirculating memory and accessed in the reverse order as printing now takes place from right to left. The third line is treated in the same way as the first, and so on. Each character may be printed in 'expanded form' when each dot column is printed a plurality of times (this feature is claimed in Specification 1,490,562. Circuitry for affecting the above and other operations (e.g. line feed) is described in detail with reference to Figs 2-6 (not shown).