Patent GB-799764-A (GB)
Title: Improvements in apparatus for selecting data from a record tape
IPC: G06F17/30
Filed: 1957-01-11
Abstract: 799,764. Electric digital-data-storage apparatus. NATIONAL CASH REGISTER CO. Jan. 11, 1957 [Jan. 11, 1956], No. 1107/57. Class 106 (1). An electrical apparatus for selecting items of data having common characteristics from a record tape store, signals sensed from the tape are compared with standard signals from an external source, and the direction of tape feed is controlled in accordance with the comparison result to locate any data item having the required common characteristics in a predetermined position with respect to the sensing device. The apparatus described is similar to that described in Specification 780,749 and may be operatively connected with a computor as described in Specification 770,952. The apparatus is controlled by a programme sequence unit comprising four bi-stable flip-flops (N1-N4, not shown) providing a different output signal for each of the 16 conditions. Only four of these (numbered 0, 14, 15, 2) are relevant to the selecting or " category search " operation of the invention, the remainder relating to search, read or record operations (not described in detail). The tape, Fig. 2, has a clock channel and four information channels Ch1-Ch4 in which decimal digits and other data are recorded in binary coded form. The information is divided into blocks each comprising 10 words W s  and W 0 -W 8 . Words W 0 -W 8  each comprise 11 digit portions D b , D 0 -D 10  and W s  comprises D b  plus blank area D 8 . The block address is recorded in W 0  and the characteristic data for a category search are recorded in W 1 , both in the 9 digit positions D 0 -D 8 . A standard select word from the associated computer 100 comprises 9 4-bit combinations on lines 105 each accompanied by a different timing signal T 0 -T 8 , whereby these combinations are set up in successive columns of register circuits 284 each comprising a thyratron 280 which is fired if it receives a positive " 1 "-representing signal on its control grid simultaneously with a timing signal on its screen grid. In operation, the sequence unit is stepped on while the multiplesensing head 130 is over blank area W 8 D 8  if a flip-flop (K1, not shown) is in a " true " state. A category search signal from the computer causes the unit to step from rest condition 0 to condition 14 in which diode gates such as 165 pass the signals on lines 105 to the register, Fig. 5. The signal T 8  steps the sequence unit to condition 15 which causes tape drive control 131, Fig. 1, to energize solenoid 155a to effect a formal drive at high speed. During the period D 0 -D 8  W 1  for each block, the signals stored in the thratron register, Fig. 5, are read out column by column via gates such as 123 and mixing networks (not shown) so as to produce digit signals B1-B4, Fig. 7, in synchronism with corresponding signals M<SP>1</SP>1-M<SP>1</SP>4 obtained from the tape; the two sets of signals are positive for " 1 " and " 0 " respectively, so that only if every " 1 " in the computer signals is accompanied by a " 1 " on the tape will no output by any of the four comparator gates such as 121. In such a case, comparison agreement is indicated and flip-flop K1 is not triggered false. The sequence unit is stepped on to condition 2 which after delay produced by a one-shot multivibrator causes unit 131 to energize solenoid 151 to reverse the tape drive. When the blank area at the beginning of the block containing the successfully compared data is reached, the tape is stopped and the sequence unit is stepped to 0 in preparation for a read operation during which solenoid 155b would be energized for forward tape drive at low speed. An example of operation is given in which the data on the tape relate to borrowers' accounts with a loan company or bank.