GB1201219A - Improvements in or relating to computing devices - Google Patents

Abstract

1,201,219. Electric selective signalling. HONEYWELL Inc. 22 July, 1968 [24 July, 19671. No. 34786/68. Heading G4H. To effect a coarse and fine digital measurement of the phase difference between two cyclic signals A, B the cycle of each of which includes a period when a carrier is modulated by a continuous wave component followed by a period of silence followed by a pulse of unmodulated carrier the A and B wave components are fed by a wave synchronizer pulsed by a clock source 56 (Fig. 1) to a sine wave counter control 16 which enables a fine wave counter 20 to accumulate clock pulses during the time interval between a B and A wave, the result of the previous measurement being held in an output fine register 56. Similarly a fine pulse counter 32 accumulates pulses between two pulse component signals, overflow pulses being accumulated in a coarse pulse counter 30. If a pulse valid signal is received the contents of coarse pulse counter 30 are transferred to coarse wave counter 38 and at the end of the cycle the contents of fine pulse counter 32 are compared with fine wave counter 20 to increment or decrement counter 38 when counter 32 has a large count and counter 20 a small count or vice versa. If a pulse valid signal is not received the contents of coarse wave counter 38 are adjusted if necessary by comparing the previous fine measurement stored in register 56 with the new measurement in counter 20 the count in counter 38 being incremented or decremented by one when the counts differ substantially depending on the relative values of the contents of counter 20 and register 56. The fine pulse counter 52 accumulates its count positively or negatively depending on whether a B or A pulse is received first. The apparatus may be used for measuring the direction of travel of acoustic waves received by three hydrophones, the hydrophones being connected in pairs to the described apparatus.