The accumulator register and the rotor.
The addition mechanism operates on a reciprocating cycle, controlled by the forward and return strokes of the operating handle.
The accumulator register and the rotor.
This view from the right-hand rear of the machine shows the register and rotor partly assembled on the inner left-hand side plate.
The rotor consists of two sectors which are spring-loaded together. The rear sector is connected to the keyboard through the long horizontal keylink, and carries the raised numerals for printing. The numerals include fixed decimal points (2 places) and thousands separators. The front rotor sector engages with the accumulator register. The "rotor" does not rotate fully, but moves back and forth through an arc of about 90°.
The register consists of two sets of eight 10-tooth gears. The upper set holds the positive total; the lower set holds the complement, and acts as an intermediate (ie, reversing) gear during subtraction. Each gear has a wide tooth at the Zero position to operate the carry mechanism.
The register is moved in and out of engagement with the rotor by a control mechanism between the left-hand side plates, and is raised or lowered by a mechanism connected to the Minus key.
The carry levers and links.
The register is shown here in its normal (lower) position.
The carry mechanism consists of a sensing finger (on the central shaft) and a sliding link with a flanged pin at its upper end. The pin passes loosely through the curved slot in the rotor. The sensing finger and the sliding link are spring-loaded (forward and upward) by a single spring, but the link is prevented from rising by a tag under the top of the sense finger.
During an addition cycle, the register rotates counter-clockwise as the rotor returns to its home position. If a digit passes from 9 to 0, the wide tooth will press upwards on the ramp on the underside of the carry sense finger. The finger will move rearward, releasing the sliding carry link on the next digit, and allowing it to rise by a distance equivalent to one tooth. The sliding links normally stop the rotor travel near the end of the stroke, but any sectors with carries pending will travel one step further and add one extra digit to the register.
There are several complications in the carry mechanism, which are described further in the Operation section.