747,470. Cash registers. NATIONAL CASH REGISTER CO. Nov. 3, 1954 [Feb. 23, 1954], No. 31798/54. Class 106 (1). In a cash register having a plurality of control keys for releasing the machine for operation and controlling entry of amounts into the appropriate side of an add/subtract totalizer, locking mechanism is effective to lock a certain one of the control keys until at least one item has been entered additively into the totalizer and a subtotal taken. The invention is applied to a machine which computes the change due on a transaction, and which includes an " Amount Tendered " key and a " Change " key in its transaction key bank 85. After entering successive items and taking a subtotal, the money received from the customer is entered by operating the " Amount Tendered " key, which selects the minus side of the totalizer to subtract the amount from the subtotal, so leaving a negative remainder representing the change. The multiple-item totalizer is then cleared by operating the " Change " key, whereupon the change is indicated and the cash drawer released. If, however, the customer tenders an exact amount, a " No Change " key is operated to clear the totalizer. The invention provides mechanism for locking the " Amount Tendered " key except when one or more positive items have been entered and a subtotal has been taken. In the machine described, moreover, the " Change " or " No Change " key alone is operable to effect the final clearance according to whether or not the multiple-item totalizer registers an overdraft. Other interlocks are provided between the control keys 85 and total lever 87 to ensure correct operation. In other respects the machine is of normal Shipley construction and includes front and rear totalizer lines as well as the add/ subtract totalizer on an upper line. The machine is released by any one of the transaction keys 85 or by a motor bar 86. " Amount Tendered " key and lock. The " Amount Tendered " key functions to select the minus side of the add/subtract item totalizer and does so by arresting the transaction differential arm 455, Fig. 16, in its zero position, the transaction differential controlling axial alignment of the totalizer wheels with the amount actuators through the usual drum cam. A pin 115, Fig. 6, on the " Amount Tendered " key stem cams a slide 591 downwardly and the slotted lower end of the slide rocks a stop pawl 594 clockwise to engage over the differential arm 455 and arrest it. The key is locked against operation except after (1) entry of one or more positive items followed by (2) a subtotal operation. This is effected, as regards (2), by abutment of a stud 600 on the pawl 594 against the edge of a slide 602 connected to a bell-crank 603 adapted to be rocked counter-clockwise and then clockwise by a main cam 608. In a subtotal operation, a stud 462, Fig. 16, on the total lever 87 comes opposite a notch 466 in an arm 460 so that a spring 463 rocks the arm about its pivot 461 to position a finger 459 in the path of a step 458 in the differential arm 455. The finger arrests the arm 455 in its fourth position and positions a slide 609, Fig. 6, connected with the transaction differential so that an abutment 610 thereon lies under a stud 611 on the bell-crank 603. This prevents return clockwise movement of the bell-crank so that the slide 602 is held raised with its abutment edge clear of the stud 600 on the stop pawl 594. As regards (1), a latch 621 normally engages over the stud 600 to lock the pawl 594 and, therefore, the " Amount Tendered " key. The latch is held energized by a pin 456 on the differential arm 455, but is released upon movement of the differential arm during entry of the positive item, whereupon a spring disengages the latch from the stud 600. The latch then remains disengaged until restored, in known manner, during an item total operation. Restoration during the item subtotal operation is prevented in the following manner: a roller 623 on an arm of the pawl engages a cam slot in a plate 625 and so rocks this plate to engage a stud 627 over a step 628 in a plate 575 secured to the total lever 87. Consequently, when the total lever is moved to the subtotal position, it raises the plate 625 on its pivot 626 and positions a nose 630 behind the roller 623 so preventing return clockwise movement of the latch 625 during the subtotal operation, the latch remaining disengaged until the concluding item total operation. Operation by the " Change " key.-Adjustment of the total lever 87 to the " Item Total " position to clear the item totalizer and register the change, locks-out the motor bar 86 and all of the transaction keys 85 except the " Change " and " No Change " keys. The arm 460 (see above) moves counterclockwise and clears a pin 546, Fig. 16, from an arm of a lever 543 pivoted at 544, whilst the existence of an overdraft on the totalizer, representing the change due, results in clockwise movement of the usual overdraft shaft 492 which clears a hook 541 from a pin 542 on the lever 543.-The lever is now free to move counterclockwise by a spring 547 and, by means of a link 550, positions a stop 556 under an arm 557 on the machine release shaft 70 to lock the machine against release. Movement of the link 550 also pushes a bar 570 adjacent the transaction key bank downwardly to position a stop 573 under a pin 115 on the " No Change " key and clear a stop 572 from a pin 115 on the " Change " key. The machine can now be released only by depressing the " Change " key, its pin 115 camming the bar 570 upwardly to move the stop 556 clear of the arm 557 on the release shaft 70. When no change is due, the overdraft shaft is not operated, the stop 556 does not lock the release shaft 70 and the stop 573 remains clear of the " No Change " key which is, therefore, operable to clear the totalizer. Printing - mechanism.- The machine is equipped with voucher and detail strip printers. These are of usual construction except that the strip printer only operates when one of the four lower transaction keys 85 is depressed or the total lever 87 is set to a total position, so that individual items of a multiple-item transaction do not appear on the detail strip. The strip 632, Fig. 20, is drawn from a supply roll 640 and past type-wheels 633 to a take-up roll 643 adapted to be driven by a feed-pawl 644 carried by a lever 646. The lever and pawl are moved in the feed direction by a power lever 649, but a hook 672 normally engages a lip 670 on an arm of the lever to prevent its return movement under the action of a spring 647 and so prevent feed of the strip. The hook 672 is fast with a lever 680, 682 connected to a slide 694 which normally underlies and disables the printing hammer 692. A roller 679 on the lever arm 680 engages a cam 678 connected with the transaction differential. When any one of the four lower transaction keys is depressed, the cam 678 depresses the lever arm 680 which withdraws the hook 672 and slide 694 so that feed movement is imparted to the strip and the hammer is effective. Movement of the total lever to a total position rocks a shaft 212 one way or the other from its normal " add " position shown. A notched arm 685 on the shaft 212 cams a stud 687 and supporting arm 688 clockwise, and a second stud 690 on the arm rocks the lever 680, 682 similarly to release the strip feed mechanism and impression hammer.