873,855. Digital electric-calculating apparatus. INTERNATIONAL COMPUTERS & TABULATORS Ltd. Oct. 9, 1959 [Nov. 10, 1958], No. 36056/58. Class 106 (1). In an accumulator which may be record-card controlled, each denominational order comprises a spindle secured to which is a toothed wheel rotated by two pawls under the control of individual electromagnets energizable by the respective positive and negative half-cycles of A.C., and there is provided a switch-actuating member locatable in each of three positions under control of a control element movable with the spindle to control opening and closing of three switches. Normally open read-out contacts, one for each digit of the denominational order are also provided. As shown, a spindle 1 has secured thereto a ratchet wheel 7, rotation of which is effected by two pawls (not shown) under the control of electromagnets responsive to respective positive and negative half-cycles of A.C., separation of the halfcycles being effected for example by rectifiers or by polarizing the electromagnets. A switch actuating member 18, pivoted at 19 has first and second laterally-extending feelers 22, 23, the feeler 22 normally resting on a control element in the form of a disc 24 also secured to the spindle 1 and having a radial slot 36. A third feeler 25 on the member 18 is adapted to co-operate with one of two steps 26, 27 on a foot 28 pivoted at 29 to a rocking saddle 30 rockable by a carry electromagnet 31. The foot 28 also carries a switch closing element 35. Normally, the member 18 is maintained in a first position by the feeler 22 resting on the face of the disc 24. When "9" is registered, however, the feeler 22 passes through the slot 36 so that the feeler 23 rests on the disc 24. Further rotation of the " 0 " position results in the second feeler 23 passing through the slot 36. The member 18 controls three switches 37, 38; 39, 40 and 41, 42, the switch 37, 38 being normally closed, and the others being normally open. The switch elements 39, 41 carry projections 43, 44, engageable with the switch closing element 35 on the foot 28. The switch element 37 contacts a pin 46 on the member 18 to urge it clockwise (Fig. 3), and when the second feeler 23 passes through the slot 36, an abutment arrests the switch element 38 to open the switch 37, 38. In operation, the digits of a number are entered in parallel and the carry electromagnets 31 are then energized. In each order the foot 28 is thereby rocked upwards to rest against a stop 33. If the feeler 22 then rests on the disc 24, the feeler 25 is riot engaged by the foot 28, and the switches 37, 38; 39, 40; 41, 42 are unaltered. If the feeler 23 rests on the disc 24 (i.e. " 9 " has been registered), the feeler 25 engages a step on the foot 28, which is thereby prevented from further rocking, the switch closing element 35 being aligned with the projection 44 so that the movement of the foot with the saddle 30 is effective to close the switch 41, 42, the other switches being unaltered. If the feeler 23 has passed through the slot 36 (i.e. a "O" has been registered), the switch 37, 38 is opened and energization of the carry electromagnet 31 results in engagement of the feeler 25 with the step 26 on the foot 28, subsequent movement of the foot with the saddle 30 closing the switch 41, 42. The pivot 19 of the member 18 is moved by the foot 28 slightly to the right (Fig. 3), so that the member 18 can be rocked by the foot 28 and restored to its original position with the feeler 22 on the disc 24. When number entry has been completed, a carry pulse on a line 68, Fig. 7, effects carries over any contacts 39, 40 which are closed, carries -on-carries being effected over any contacts 41, 42 which are closed. Read-out arrangements.-Normally open readout contacts 49, 50, one pair for each digit, are spaced round the spindle 1. When readout is required, an electromagnet 53 is energized, thereby depressing the spindle axially downwards, an arm 52 on the spindle closing the appropriate contacts 49, 50. In the event that the digit read is "O," a second arm 57 also fixed to the spindle 1 closes contacts 58, 59 which control printing of zeros. Checking arrangements.-In each denomintion the arrangements described are duplicated, a spindle 1a coaxial with the spindle 1 being arranged to be rotated in the reverse direction to the spindle 1 by an amount corresponding to the complement of digit registered by the spindle 1. The spindles 1, 1a are coupled by levers 60, 61 which are parallel when both spindles register "O." When a digit and its complement have been correctly registered by the spindles 1, 1a, the levers 60, 61 are again parallel and thus on axial movement of the spindle 1, axial movement is imparted to the spindle 1a only if the registered values are correct. The spindle 1a can be made to control an electric contact.