Patent GB-769650-A (GB)
Title: Electronic record card verifier
IPC: G06F7/02
Filed: 1955-05-13
Abstract: 769,650. Statistical apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. May 13, 1955 [May 17, 1954], No. 13871/55. Class 106 (1). Verifying card perforations.-A machine for verifying card perforations at a plurality of index positions in successive columns of a record card comprises an electrical circuit including, for each card index position, a pair of electronic valves, one of each pair of valves being adapted to change from an initial, to an alternative state of conduction in response to the sensing of a perforation by an associated sensing brush and the other of each pair of valves being similarly adapted to change its state when an associated manually operable key is actuated, each pair of valves being so interconnected that no change of their states occurs when a perforation is sensed simultaneously with actuation of a corresponding. contact, and an escapement mechanism governing advance of the card from column to column being connected in said circuit so as to be operable only when all the valves are in their initial states. In the form described, the pairs of valves are enclosed in a single envelope. As shown in the Figure a set of keys 22 is provided, each of which when pressed closes a key contact 23, there being double contacts for each alphabetical key and a single contact for each numerical key (each alphabetical character is designated by a perforation in one of the index positions 1-9 and also a perforation in one of the positions 0, 11, or 12). The keyboard is also provided with bail contacts 24 which close after each selected set of character-representing key contacts 23 and open before these contacts break. Each contact 23 is connected between one of the left-hand cathodes and earth. The cards C pass over an earthed roller 27 and are sensed by brushes 25 adapted to pass through perforations 26 and contact the earthed roller. Each brush is connected to one of the righthand cathodes. The pairs of valves are interconnected. so as. to act as an "exclusive" or gate and are termed OR-0 to OR-12. For each pair of valves two voltage dividers are provided, each consisting of three equal resistors 36, 37, 38 and 41, 42, 43 connected between a source of + 150 volts at one end and - 50 volts at the other. The connection points la and ra are therefore at about +83 volts and points lb and rb are at about + 17 volts. The left and right-hand grids are connected to points.lb, rb respectively and the left and righthand cathodes are cross-connected to points ra and la respectively. Normally, both cathodes are therefore at +83 volts and both grids at + 17 volts so neither valve conducts. However, when a left-hand cathode is connected to earth by the key contact 23, point ra connected to point rb is earthed and the right-hand grid therefore has a voltage of - 25 volts. Since the left-hand cathode is earthed and the grid is still at +17 volts this valve conducts. The right-hand valve does not conduct since the grid is still less positive than the cathode. If both cathodes are simultaneously earthed as would be the case where the character selected by the keys agreed with the perforation sensed, both grids become negative (- 25 volts) and so neither valve conducts. The failure to agree is therefore shown by conduction of one of the valves. All anodes are connected together by line 47 which is connected through a resistor 51 (20 K.) to the +150 volt supply, and through a voltage divider comprising resistors 54 (200 K.) and 56 (100 K.) to the - 50 volt supply. The junction 55 is connected to the grid of a thyratron 57 and this is normally at about +17 volts so that the thyratron fires when bail contacts 54 close to energize escape magnet 30 thereby advancing the card one column. When one of the valves is conducting due to a failure to agree, a drop of 100 volts occurs across resistor 51 so that point 48 is now at about +50 volts, and the potential of point 55 falls to about -17 volts. This prevents the thyratron firing and no advance of the record card can take place.