Data synchronizer for use with a variable rate input source

Abstract

A digital system is disclosed for synchronizing data in a variable-rate pulse stream, as by the intervals of a magnetic recording medium. Functionally, an estimate is made of the size of a repeatedly recorded interval and the estimate is registered. In subsequent operation, the estimate is revised whenever it is found to differ from the recorded interval, based on an allowable tolerance. The revision is by a fixed percentage of the registered estimate. An oscillator drives a down counter which is variably pre-set in accordance with the prior timing history of the pulse stream (including a substantial number of pulses). Accordingly, each cycle of the down counter provides a variable sub-interval, a predetermined number of which are counted to provide each variable synchronizing interval. Comparisons of the synchronizing interval and the pulse stream serve to adjust pre-setting of the down counter to a current value. An analog form of the system is suggested and techniques are disclosed for use of the system with various pulse code formats.