GB1459816A - Printer - Google Patents

Abstract

1459816 Control of printers SINGER CO 27 Dec 1973 [5 Jan 1973] 59815/73 Heading G4H A dot matrix printer 12 comprising one or more print carriages is capable of printing in both directions of motion of the carriage(s). It may incorporate means 60 for ensuring alignment of printed characters. As described, printer 12 comprises two 7-wire printheads 56, 58 for printing 9 Î 7 matrix characters on two out of three record media 36, 38, 46 simultaneously (e.g., a bill of sale and an audit trail in an electronic cash register). As the printer moves back and forth across the media, photosensors co-operate with coded apertures in a bar 60, Fig. 3A, to generate character strobe signals 71, 73 each of which triggers a one-shot 81, Figs. 5A (not shown). The trailing edge of the one-shot output initiates the printing of a new character on both media, the time for this being divided into 14 column times, Fig. 4. Each column time is divided into "A" and "B" halves for alternate printing on the two media. Data is input from a keyboard to a recirculating shift register (91) whence it is used to access a read-only memory (92) which produces printhead character control signals. The output from one shot 81 starts up and down counters (for left/right and right/left printer movement) which cause a multiplexer (86) to send alternate control signals to ROM (92). A comparator (88) compares the printer position 71 or 73 with the print positions of the characters at the output of register (91) in turn, and controls latch circuits (93) located between ROM (92) and the printheads (94), which are enabled alternately by sync. signals # A , # B , Fig. 4. The printer may include means for printing data upside-down on one of the media (e.g. for summing a bill).