Apparatus for aligning word interval signals with the word frame of received digital data

Claim 1

Apparatus for aligning frame interval signals with the word framework of received serial digital data consisting of words each having same number, at least three, of digits, the coding of the words being such that at least one possible word length group of digits is not permitted in a word of the received data, the apparatus including; means for producing a clock signal from the received data; interval-defining means producing signals defining frame intervals in response to the clock signal; alignment-indication means responsive to the detection of a notpermitted group of digits in the received data overlapping parts of consecutive frames as defined by the frame interval signals to produce an indication of alignment; nonalignment-indication means responsive to the detection of a not-permitted group of digits in the received data within a frame interval as defined by the frame interval signals to produce an indication of nonalignment; storage means storing a total and responsive to the indication of alignment to modify the stored total by a first weight and responsive to the indication of nonalignment to modify the stored total by a second weight having an opposite effect to the first weight; the weights being such that a single indication of alignment does not always cancel the effect of previous occurrences of the indication of nonalignment; and phase-shifting means responsive to the total in the storage means to shift the phase of the frame interval signals relative to the received data when the total attains a threshold value.