692,096. Typewriters &c. BURROUGHS ADDING MACHINE CO. March 3, 1950 [March 8, 1949], No. 5445/50. Class 100(iv) An electromagnetically controlled printing mechanism comprises a series of printing elements, a series of print-control elements (rods 41, Fig. 4) for moving the printing elements to printing position, means e.g. bail 53 for retracting the rods 41, an armature 47 for each rod movable by its rod to a location where it may be retained by an electromagnet 38, and means for selectively energizing or not energizing the magnets 38 so that the appropriate rods 41 may be moved to effect printing by the elements. The printing elements comprise fine wires 30 which are arranged in groups of thirty-five Fig. 12 (not shown) for each print head 29, as described in Specification 674,343. The machine which is controlled by record cards comprises a number of printing heads 29 arranged in groups of six Fig. 1, to form two characters in each of three lines, and positioned in an end portion 20 of a block 19, Fig. 2, constituting the front of a narrow panel 18. A sensing of each record card effects the setting of all mechanisms to effect printing simultaneously in the three lines. The wires 30 from each group of six are guided through tubes into six control units 35 on one panel 18, and a number of similar panels 18, Fig. 1, are mounted together between side plates 15 and 16 connected by tie-rods 17. Each unit 35 is divided into eighteen sections, Fig. 2, each having two control electromagnets 38 excepting the extreme righthand section which has one magnet. The magnets are mounted on inclined supporting bars 36 so that the print control elements or rods 41, Fig. 4, forming extensions of the wires 30 are conveniently arranged to coact with the armatures 47 of magnets 38. Each rod 41 is urged to move its wire 30 into print position by a spring 44 but during a cyclic movement of a bail 53 into dotted line position the rods 41 are moved into non-print position and a collar 51 on each rod engages behind a shoulder 52 on the armature 47 of its associated electromagnet 38 and thus closes the air-gap A. At this point in time the record card is sensed and the electromagnets 38 are selectively energized and maintain the airgaps closed so that the cyclic movement of the bail 53 will allow the rods 41 of such operated magnets to move under the action of springs 44 into print position. Those magnets not operated will release their armatures 47 and shoulders 49 thereon move in front of a second collar 50 on each of the rods 41 which are thus held in non- print position. In an alternative arrangement, Fig. 6a, (not shown) the reverse operation is effected wherein those electromagnets whose printing elements are to be prevented from advancing to print position are energized. The bail 53 in both cases is slidable in a block 24 in each panel 18 and cyclically operated by bell crank levers 55 engaged by arms 58, one pair for each bail 53, and which are mounted on common rock shafts 56, 57 journaled in the side plates, 15, 16 and oscillated by cam mechanisms 61-68 from a powered shaft 60. The thirty-five electromagnets 38 for each printing head are selectively operated in various combinations in accordance with a code as decribed in Specification 674,343, in which perforations in rows 12, 11 and 0 of associated record cards select groups of letters, and perforations in rows 1-9 select letters within each group, or figures if not preceded by a group code. If, e.g. a letter A is to be printed, perforations occur in rows 12 and 1 of the record card. Sensing of perforation 12 by a column sensing brush 74 puts an increased bias on to the centre point of one half of a bridge network between grid and negative potential of a series of thyratrons 76-78, 86-94 corresponding to the rows 12-0, 1-9. If, at the same moment of sensing a perforation by the brush 74, a distributer 75 rotating in step with the sensing of the rows of perforations in the record card puts an increased potential on to one of the thyratrons 76-78, then that thyratron, say 76, receiving the increase potential on both halves of the bridge network now fires and a circuit (e.g. in the case of letter A) is extended from positive, wire 97, cam 61, relay 79, thyratron 76, relay 83 to zero volts. Relay 79 is thus operated and closes contacts in circuits associated with electromagnets 38 required to form letters within group A-I. Sensing of the second perforation (row 1) by brush 74 causes, by a similar arrangement, one of the thyratrons 86-94 to fire, e.g. thyratron 86 in the case of letter A, and complete a circuit from zero volts, relay 110, thyratron 86, contacts A (now closed), wires 95, electromagnets 38 required to make up the letter A, wire 70, print cam C4, wire 97, to positive battery. The thyratrons are stopped by holding cams Cl and C2 which remove the positive potential from the anodes. In order to prevent the printing of a numeral on receiving the second letter code the operation of any one of the thyratrons 76-78 causes a common cathode relay 83 to operate opening contacts 84 in a circuit to a relay 82 so that when the second code of a letter is received the numeral magnets 38 are not operated. When numerals are to be printed contacts 84 remain closed, because none of the thyratrons 76-78 are operated, and the relay 82 is thus able to be operated by a numeral cam C3. Relay 82 closes contacts 1-9, Fig. 9, extending connections to the various conductors 71 connected to the printing magnets 38. The subsequent numeral code operating its particular thyratron causes the operation of the particular magnets 38 through the connection set up. The same type elements are used to form both the letter O and zero, but the selection thereof is arranged differently. The letter is formed as a result of perforations in rows 11 and 6 and zero from row 0 only, the former being arranged by firing thyratrons 77 and 91 in a similar manner to that described above in connection with the letter A. When a code is in row 0 only, zoning thyratron 78 is fired, operating relay 81; this closes contacts S-Z but this has no effect since no second perforation is present to fire one of the numeral thyratrons 86-94. Relay 81 however has an additional contact 111 which completes the circuits from the 0 electromagnets, through wire 112, contact 111, resting contacts 113 of relay 110 (not operated), link 115 and through a zero print cam C5: Specification 692,137 relating to the suppression of the printing of zeros is referred to.