Patent GB-732345-A (GB)
Title: Improvements in or relating to means for checking recorded information
Inventor: WRIGHT ESMOND PHILIP GOODWIN
IPC: H04L17/30
Filed: 1949-12-02
Abstract: 732,345. Statistical apparatus. STANDARD TELEPHONES & CABLES, Ltd. Oct. 26, 1950 [Dec. 2, 1949], No. 26117/50. Divided out of 732,341. Class 106 (1). Apparatus for checking information recorded in printing telegraph code on a magnetic recording medium, comprises a teleprinter for supplying a reference version of the information to be checked, a play-out device for extracting this information from the recording medium character by character, first and second storage circuits in which a reference version character from the teleprinter and the corresponding character from the recording medium are respectively inserted, a comparator circuit for comparing characters in the storage circuits, an alarm arranged to operate if the comparator circuit detects a difference between corresponding characters, a recording head, and means for applying a character to the recording head if the comparator gives no indication of difference between that character and the corresponding reference version character from the teleprinter. The arrangement of the apparatus is shown in Fig. 1. A tape machine 1 of the type described in Specification 685,032, [Group XL (b),] is fitted with magnetic tape upon which the data to be checked has been recorded in startstop, mark-space, telegraphic code. Upon switching on, the tape is played out until the reproducing head 9 picks up the start element of the " start S " signal which precedes the data recorded. The start element appears as a signal on an " S " lead from a known modulator gate (Fig. 2, not shown) and, via gating circuits of the type described in Specification 636,700, [Group XL (c)], trips a cold-cathode trigger pair and thereby sends a positive pulse to start the recorder's time scale 7 which is of the type described in Specification 692,436. The checker now enters the " start S " on a teleprinter 2 and this is set up in the checker's register 3 under control of the checker's time scale 4 which also causes the play-out clutch 6 to engage whereby the " start S " recorded on the tape is read into the recorder's register 8. Both registers 3 and 8 are of the type described in Specification 663,574, [Group XL (b)]. When the checker enters each subsequent character the play-out clutch 6 is engaged to read out the corresponding character from the tape and, when the stop element is reached, the contents of the registers 3 and 8 are interchanged via a transfer network and, under the control of a unit 10, compared element by element. During the entry of the next character the first character is driven out of the checker's register 3 to be printed on the teleprinter reference sheet, and driven out of the recorder's register 8 to be re-recorded on the magnetic tape. This, of course, is when no error is revealed ; in the event of a disagreement being detected by the comparator 10, a gate 17 is opened to prevent printing and the device 17 operates to enter " Line feed " into the checker's register 3 and then "Alarm." Provision is made for correcting errors, inserting new data, and removing redundant data. Comparator circuit, Fig. 13. The normal condition after a correct comparison is with tubes CA and CC discharging and tubes CB and CD extinguished. The existence of a " space " element in the recorder's register at the time of comparison causes a rectifier W42 to be biased positively and, when the other rectifiers become biased by timing voltages &c., a positive impulse is transmitted to the trigger element of the tube CB to cause it to fire and extinguish the tube CA. If the corresponding element in the checker's register is a " space," a positive impulse appears at the trigger element of the tube CA and re-fires it, extinguishing the tube CB. Where both compared elements are " marks " no firing of the tubes CA, CB occurs. When different elements are compared the tube CB is left in the discharging state and this subsequently causes CD to fire, indicating that a discrepancy exists. Specification 692,415 also is referred to.