The demonstrative animation here is explained in detail in the text underneath it.
The Forward Stroke
A bank clerk depresses key (a) and pulls the operating lever of the machine forward.
The action of pulling the lever causes a sector (b) to swivel round on a pivot at its center.
The projection (c) attached to the pivoting sector descends.
As the projection (c) descends, the rack (d) at its top descends as well.
The descent of rack (d) is brought to a stop by wire (e).
Wire (e) acts as the "depressor" because it is attached to key (a), which was pressed by the bank clerk using the adding machine in step 1.
Meanwhile, on the other side of the pivoting sector:
The other end of the pivoting sector (b) is equipped with typefaces, which correspond to the keys in the column under which the sector is operating.
When the movement of the sector (b) is halted by the wire (e), the typeface which corresponds to key (a) is opposite the printing space. In this case, it is typeface 6.
At the end of the handle's forward stroke the printing of the sum entered in step 1 takes place.
The Reverse Stroke
When the bank clerk pulled the machine's handle at the beginning of the operation, he caused a pinion bar to withdraw and take the recording pinion (g) out of gear with the rack (d), mentioned in step 4 of the "Forward Stroke" process.
The bank clerk now begins to return the operating lever to its original position, throwing the recording pinion (g) into gear with the rack (d).
As the rack (d) returns to its starting position, the recording pinion turns through just six spaces (in this case, it turns through 6 spaces because, as you remember from step 2 in the "Pivoting Sector" section above, the bank clerk initially pressed down on key number 6).