683,857. Statistical apparatus. COMPAGNIE DES MACHINES BULL. Dec. 20, 1950 [Dec. 29, 1949], No. 31081/50. Class 106 (i). In a collating machine for re-constituting a card index in numerical order from which certain cards have been removed, two packs of cards are placed in hoppers 355 and 356, Fig. 1, being termed secondary and primary respectively, comparison is made of the readings obtained at reading stations BS1 and BP2 and the lower card numerically is fed forward first by electromagnetic clutches controlling the feeding arrangements associated with each reading station. The comparison is effected according to the invention by recording units for recording data from the cards, each recording unit comprising a distributer device, a series of gaseous discharge tubes adapted separately to be rendered conductive by an impulse passing from the reading means through the distributer device to the tubes of a unit, the tubes of each unit having anode circuits including resistances of different values, and a common cathode circuit for all tubes of a unit across which is generated a voltage proportional to the magnitude of the data read, and comparing means common to all the recording units for comparing the voltages developed across the common cathode resistors of each unit, and means for controlling the subsequent operation of the machine accordingly, Fig. 2b (lower part) shows the two reading stations BP2 and BS1 connected by 504 and 507 respectively to the common bus-bars of two rotary distributers having brushes 88 sweeping the individual contacts in timed relationship. The individual contacts are connected each to the grid of a separate thyratron, the grids being also connected to a negative bias line 508 so that they are normally inactive. An over-riding positive impulse is transmitted to the grid of a thyratron when a hole is detected according to the value represented, by a timed pulse travelling from the positive 80 volt line 517 via impulse generators 77 or 111, common brush 623, jumper 504, or 507, distributer 88 to the grid of the tube representing the number detected, whereupon the tube fires and draws anode current. The anode load resistors are unequal and are graded so that most current is drawn by the thyratron representing 9 and the least by that representing 1. The voltage developed across the common cathode resistor RKUP or RKUS represents the value of the number detected and may for example vary in 3 volt steps from 3 to 27 volts according to the value 1 to 9, zero being represented by no hole in the card and all thyratrons inactive. Comparison of the voltage in each pair of cathode resistors RKUP, RKUS, representing units and RKUP and RKDS representing tens is made in succession by connecting each pair in timed sequence to a cathode coupled balanced pair of pentode valves VP, VS, Fig. 2a. The contacts CGP, CGS, UDC, top of Fig. 2b, representing units, tens, hundreds, and so on, are operated in timed relationship, priority being given to the highest denomination. Uneven voltages developed across a pair of cathode resistors cause, when connected to the grids of the valves VP, VS, at the appropriate time, an unbalanced condition in which the anode current of one valve increases and the other decreases according to which grid is driven more positive by the greater voltage developed across the common cathode resistor, with the result that the balanced relay 500 is moved to the left or right (Fig. 2a), and actuates relay RP or RS. Movement of relay RP or RS actuates their respective contacts RPc RSc in the lines 515, 516, to the unit thyratrons so that the lower reading is removed by the interruption of the anode current, and the limit is accordingly re-set to receive the next reading for comparison with the higher recording which is retained until the next cycle, for this purpose. Energization of relay RP or RS also changes over contacts RBd, RBe and RSd, RSe, respectively to energize one of the three relays 334, 335, 339 (Fig. 2a, top). The appropriate relay is energized closing one of the sets of contacts supplied by CG5 which is closed at the end of the cycle, and which supplies the energizing voltage via these relay contacts, for example, 335c, to line EAP and clutch magnet EAP which clutches the primary feed shaft to the main shaft and causes the primary card to be fed forward first, or alternatively via contacts 339b and jumper 494 to line EAS and to the clutch magnet EAS which actuates the clutch, causing the recording card to be fed forward first. In the case where equality exists between the compared voltages, or there is no reading recorded on either unit, neither relay RP nor RS is energized and the contacts RPd, RSd remain closed as shown in Fig. 2a, causing relay 334 to be energized, resulting in both drive clutches EAP and EAS being actuated together. Priority is given by the timing of the contacts CGP, CGS, CDU so that the highest denomination is compared first, as soon as one of the relays RP or RS is energized, contacts RPb and f, or RSb and f, are opened, opening the grid circuits to the balanced pins of valves VP, VS, so that lower denominations are ineffective, and the machine responds to the highest denomination difference. In a modification described a balanced pair of valves with associated relay 500 is provided for each denomination so that the timed relationship referred to above is not followed, all denominations being compared simultaneously. In this case the relays actuated by the relays 500 are RPU, RSU, RPD, RSD, &c. and are arranged in a chain circuit, Fig. 3b, having one input and three outputs identical to that described in connection with Fig. 2a. This chain ensures that on the simultaneous comparison of all denominations the highest order will take priority and be effective for controlling the subsequent functions of the machine. A further modification, to obtain economy of valve circuits may be employed with a code employing one or more perforations in a card. For example, numbers 1-4 are represented by perforations 1-4, 5 by 4 and 1 and so on up to 9 which is represented by perforations 4+3+2. In this case four thyratrons only are employed in place of each set of nine previously employed. The thyratrons are fired according to the punching on the card and the voltage developed across the common cathode resistor is proportional to the sum of all the thyratrons which are active and the total volt drop produced across the common cathode resistor is the same as in the previous case. Comparison of the two cathode voltages then proceeds as in the previous case. Specification 636,911 is referred to.