GB1265327A - - Google Patents

Abstract

1,265,327. Selective signalling. BURROUGHS CORP. 1 April, 1969 [29 April, 1968], No. 16950/69. Heading G4H. In a printer of the type in which a counter 11, Fig. 1, records the position of a printing head 10, 19 by counting pulses produced inductively 26, 34 by rotation of a printing head drive shaft 14, initial synchronism between the counter and the actual position of the printing head is achieved when the system is turned on by driving the printing head to an extreme right-hand end stop 22 and then entering into the counter the number that happens to correspond to that position of the printing head. The arrival of the printing head at the end stop is detected by detecting when the drive shaft ceases to move, this being achieved by sampling the output 36 of the displacement representing pulse generator 26, 34 by clock pulses produced 63, 66 by a rotating disc 64, the sampling frequency being such that if the drive shaft is moving a change in the pulse generator output 36 will be detected before four samples have occurred, whereas if the drive shaft is not moving a change is not detected and a two-stage binary counter 40 reaches a count of four, and the appropriate number is set into the counter 11.