GB1056906A - Fully checked electronic printing system - Google Patents

Abstract

1,056,906. Electronic printer control. ANELEX CORPORATION. June 30, 1965 [Sept. 1. 1964], No. 27629/65. Heading G4H. A line printer control circuit includes means for detecting incorrect operation of the print hammers and for detecting when printing of a stored character has been omitted. A line of coded characters is stored in a core matrix (14), Fig. 3a (not shown), and as a character on the continuously rotating type drum enters the printing position, a photo-electric shaft encoder (9) produces the corresponding coded character for successive comparison at (18) with all the characters stored in matrix (14). When code agreement is detected the appropriate print hammers arc actuated by means of distributer gates (39), Fig. 3b (not shown), and gates (25) are inhibited to prevent re-entry of the character in matrix (14). The process is repeated for succeeding characters on the type drum so that, when all characters in the line have been printed, matrix (14) is empty. The delayed print-actuating pulses and the code agreement pulses are supplied to OR gate (OR3), Fig. 3b, which, if a print hammer is correctly operated, produces two successive pulses to set and reset bi-stable circuit (FF5). If a hammer fails to operate, following an agreement pulse or operates when no agreement pulse has been produced, an alarm signal is produced by AND gate (A6): In the character cycle following printing of the last character remaining in matrix (14) OR gate (OR2), Fig. 3b, does not produce an output to set (FF2) and at the end of this character cycle AND gate (A4) produces a " print complete " signal which may be used to initiate printing of the next line, i.e. the line cycle may be terminated before the print drum has completed one revolution from the start of the cycle. If (OR2) is still producing an output after the type drum has performed one revolution (timed by timer (31)) a further alarm signal is developed by AND gate (A5) signifying that not all characters in the line have been printed. This alarm may be used to cause printing of a special character signifying an illegitimate character in matrix (14).