731,620. Calculating-apparatus. VICTOR ADDING MACHINE CO. Sept. 15, 1952 [Sept. 20, 1951], No. 23111/52. Class 106 (1). Interlock mechanism between two depressible and one or more pivoted control keys in a calculating machine comprises a locking arm moved into alternative positions by projections in the stems of the depressible keys on actuation of these keys and means associated with the locking arm whereby operation of either depressible key locks the pivoted key or keys and operation of a pivoted key locks the depressible keys. Control key interlocks.-Studs 74, 76, Fig. 3, in the add and subtract starting keys 22, 24, co-operate with an arm 78 to prevent simultaneous depression of these keys. The stud 76 also co-operates with a slide 82 which is thus held to the right when the subtract key 24 is depressed. A stud 80 in the arm 78 holds the slide in this position when the add key 22 is depressed. Operation of either a total-andsubtotal key lever 26 coupled to a crank 118, or a non-add key lever, Fig. 8 (not shown), coupled to a crank 98, is thus prevented, studs 122, 96, in the cranks engaging a notch in an arm 92 carrying a stud 90 contacted by the slide 82, and a cam-surface 94, of the slide, respectively. When either of these key levers is operated, the slide 82 is moved to the left to prevent operation of either of the add and subtract keys. The stud 96 co-operates with the upper end of the arm 92 to prevent simultaneous operation of the two key levers. Locking total-and-subtotal key lever. When this lever 26, Fig. 9, is rocked in either direction, a latch 202 engages a notch 208 or 250 in the lever. On operation of the machine, a plate 218 is rocked by a cam and rocks the key lever slightly to a fully operated position. The plate also engages a stud 228, in the latch 202 to withdraw the latch. from the key lever and allow it to be engaged by a keeper 230. At the end of the operation, the key lever is released by the plate 218 and centralized by its spring 105, and the keeper 230 is rocked to release the latch 202. The latch 202 is held inoperative by a stud 248 in an upwardly urged slide 242 if a hood 176 normally surrounding the key lever is raised. Starting mechanism. Safety switch. Projections 50 on the stems of the add and subtract keys 22, 24, co-operate with a lever 54 which through a lever 58 depresses a switchoperating slide 64 when either of these keys is depressed. A stud 140 in the crank 118 engages a cam surface of a lever, Fig. 7 (not shown), to rock this lever in a given direction when the total-and-subtotal key lever is rocked in either direction. The lever is coupled to an arm which engages a stud in the upper end of the slide 64 and depresses this slide. The crank 98 is coupled to the same arm so that the slide is operated when the non-add key lever is rocked. When the hood 176, Fig. 18, is rocked upwardly about its hinge 178, a stud 184, carried thereby rocks an arm 188 to open a safety switch in the motor circuit. Symbol printing. A stud 266, Fig. 13, in the key lever 26 passes through a slot 264 in a segment 260 and is normally engaged in a notch of a slide 270 mounted on the segment. When the lever is set for a total or sub-total operation, the segment is thus rocked in one direction or the other so as to position an appropriate type in the printing position. When the sub-tract key 24 is depressed, a lever 287 is able to rock over a stud 292 in the key stem and rocks a coupling latch 304 to couple a lever 306, 312 to a cam-controlled arm 300. During the operation, the lever 312, through a lever 314, rocks a lever 321, to lower the coupling slide 270 on the segment 260 and to rock the segment to position a minus-sign type for printing. Rocking of the non-add key lever rocks a shaft 286 and an arm 284 thereon lowers the coupling slide 270. A spring 278 then rocks the segment to the extent permitted by the slot 264 to position an appropriate type for printing.