Abstract: In an associative memory, each cell 20 (FIG. 2) includes a recirculatory shift register 30 in which information is stored, a comparator 31 for comparing the stored information with a key fed on line 22, a gate 32 for passing the results of the comparison only in a key field defined by key field signals on line 23, and a flip-flop 33 which is set to 1 if the comparison fails. Flip-flop 33 controls reading from the cell. A flip-flop 37 is used to record whether the cell is full or empty, and a compare chain 40a, 40b passing through all cells in sequence is energized onwards from the first cell in which comparison is successful.A further development permits sequential retrieval and searching for the next key above a desired key if the desired key itself is not in the memory.

Abstract: A self-clocking punched record reader for reading a record (10 ) without sprocket (clock) holes has two sets of sensors (RH1) and (RH2), sensing overlapping areas in the record columns, in a read head (12). A strobe allow flip-flop (SA1) determines when at least one sensor of each set is reading a hole, and a comparator (EQ1) determines when the two sets have identical outputs. The outputs from (SA1) and (EQ1) are combined to fire a one-shot (OS1) which gives a strobe pulse (STR) output, also gating the output from sensor set (RH2) as DATA. An error flip-flop (ER1) is arranged to detect double strobing (DST) and strobe failure (no strobe, (NST).