Patent GB-855712-A (GB)
Title: Improvements in or relating to a skew compensating system for reproducing parallel recorded information
IPC: G11B20/16
Filed: 1957-02-06
Abstract: 855,712. Electric digital-datastorage apparatus. SPERRY RAND CORPORATION. Feb. 6, 1957 [Feb. 6, 1956], No. 4162/57. Class 106 (1). In a skew compensating reproducing system for reading parallel information tracks recorded, together with a pair of spaced parallel control tracks, on a storage member, e.g. a tape or drum, signals from the tracks are derived by a transducer and the information signals are passed to plural stage shift registers, the information signals being shifted in response to signals from the leading control track and being read out in response to signals from the lagging control tracks. As shown, channels 11-19 on a magnetic tape 10 are used by elements 21-29 of a transducer 20 whose outputs are passed to amplifiers A 1 -A 9 . The outermost channels 11 and 19 contain the control or sprocket signals which are passed to a timing control network comprising bi-stable flip-flops FF-1 to FF-4 and gates G 1 -G 8 ; the flip-flops are responsive to a lower signal amplitude than the gates, whereby the latter may be pre-conditioned by the same signals as are applied to their inputs. The network is such that if a number of sprocket signals appear in one channel before they appear in the other, indicating skew, a " 1 " normally in stage R80 of a shift register 45 is shifted a corresponding number of steps to the left or right, by supplying the signals to line 43 or 44 respectively. The remaining channels 12-18 contain information signals which are passed to shift registers 52-46 respectively, each of which has a separate output gate for each stage connected to a common output line L7-L1. The sprocket signals from the leading channel are applied via buffer B 1  to a counter 101 and through a further buffer B 3  to the shift pulse input line 41 for the information shift registers, and the sprocket signals from the lagging channel are applied via buffer B 2  and line 105 to gates G 80 -G 87 , G 91 -G 97  each controlled by a corresponding stage of register 45. Each of these gates corresponds to a different degree of skew and is coupled by a diode buffer matrix (Fig. 3, not shown), to predetermined output gates one for each of the registers 46-52. If, e.g. the skew is such that channel 11 is advanced three sprocket signals relative to channel 19, then the " 1 " in register 45 is shifted to stage R83, thus opening gate G83 which is coupled to shift register output gates G 10 , G 21 , G 31 , G 42 , G 52 , G 62 , G 73  as indicated. Thus for every signal on line 105, the information stored in the corresponding register stages (R10, R21 ... R73) is passed simultaneously to line L1 ... L7. When counter 101 has received all the leading sprocket signals, corresponding to an information word, it opens gate G 9  whereby the remaining lagging sprocket signals also are applied through B 3  to cause further shifts in registers 46-52. When the lagging sprocket pulses also cease, a delay flop 100 resets thus applying resetting signals to counter 101, flip-flops FF-1 to FF-4 and register 45. The system is then ready to receive and re-synchronize a further word. Reference is made to tape having information recorded as holes or as optically observable marks.