GB1350555A - Error detecting apparatus - Google Patents

Abstract

1350555 Selective signalling SIEMENS AG 12 Jan 1972 [12 Jan 1971] 1526/72 Heading G4H Apparatus for selecting the group of signals having the fewest errors from nominally identical groups of signals includes means for detecting and counting the errors occurring in each group in turn and storage means 7 which stores that group of signals having fewer errors than any one of the groups whose errors have previously been detected and counted. Groups of twelve signals in (2/5) code are input at 5 to stores 51, 53 and to a circuit 54 which feeds an error signal 11111 to an OR-gate 55 whenever a signal does not have exactly two l's, gate 55 also receiving this error signal if corresponding signals in any two successive groups are not found by a comparator 52 to be the same: in either case the faulty signal is replaced in 53 by the error signal and a counter 6 is incremented. An AND-gate 56 is enabled whenever the group then in 53 contains fewer errors than a group already in store 7, this latter group having been checked for errors by a circuit 71 and a second counter 8 correspondingly incremented: the counts from 6 and 8 are fed to a comparator 62 which sets a flip-flop 61 if count (6) < count (8) on the occurrence of a clock pulse N2 (counter 8 is initially set at its maximum value so that the first signal group may pass through gate 56). After each signal group has been tested to see whether it is a new fewest-errors group (and, if so, allowed to replace the previous group in 7), a pulse N3 resets counters 6 and 8 (if 61 has been set), then a pulse N1 resets 61. Whenever count (6) is a maximum its output 601 increments a control counter 9 via an AND-gate 92 which is enabled if count (8) has not exceeded a maximum error level set on switches 82. Counter 9 is reset by N2 if count (6) is not at that moment a maximum; if it is, then count (9) continues to increase until it reaches a preset level, whereupon its output 901 effects the transfer from store 7 of the final fewest-error group.