This view of the completed addition unit shows the front end of the horizontal key links, which connect to the keyboard via the small flanged pins at their top front corners.

The keylinks are supported by a slotted guide plate, and are held under constant rearward tension by the long coil springs in the base of the machine.

The links are restrained from moving rearward by a bail or rod which travels horizontally in the slots near the front of the side plates. The bail is connected through the curved links to arms on either side of the mainshaft. On the forward stroke, the bail moves rearward, and the key links follow under spring tension until stopped by the keyboard.

Immediately below the keyboard is a second set of sliding links, supported on two horizontal cross rails between the outer side plates. Adapter plates connect these links across and down to the pins on the fronts of the corresponding keylinks. Each pair of links then moves as a unit, with the adapter plates simply matching the keyboard column spacing (11/16") to that of the mechanism (5mm).

The tags along each side of the sliding links interact with tags on the bottoms of the key stems to limit the travel of the keylinks on the forward stroke. Note that pressing a numeral key does not cause any immediate action in the body of the machine. The key simply acts as a stop to limit the rearward motion of the corresponding keylink, thus setting the position to which the numeral sector can rise.

This detail view from the front of the machine shows four key columns, with their key stems and sliding transfer links. The holes along the front face of the keyboard contain the ends of the longitudinal key springs (secured by a brass wire), and the end pivots and tension springs for the column locking bars.

The two columns to the left are at Zero with no keys pressed. The vertical extensions on the front of the locking bars stand to the left, preventing the sliding links moving rearward. The other two columns are shown with the front keys down. The locking bar is pushed to the right, allowing the link to move rearward until the first of the sideways tags contacts the tag on the lowered key stem.

The "sawtooth" bar at the bottom pivots rearwards during the machine cycle, blocking the movement of the locking bars and preventing further keyboard entries. Another bar at the rear of the keyboard releases all the column locking bars at the end of the machine cycle.