The "Dash Pot" on the side slows the spring down to keep from slamming into position. There is a small leather cup inside and a small hole in the piston/plunger to release air at a slower rate. That is what slows the spring action.
There is also a computer that does not use the dashpot though it may be added. Most of the time they are in Tokheim pumps and are referred to as "SLAMBACKS"
The spring will not be slowed by the dash pot and keep your fingers clear when you reset!!!!!
On a semi auto,, you load the spring with one coupling and release it with the other....when you release the spring it will reset and be ready to count....if you do not understand the order in which it works and do not have it in the run position you may not be able to make it work right.
Do not rely on what or how many wheels to identify these types of computers.
The way to identify is by the reset mechs on the side.
There are Through Shafts, Extended Center Shafts, Semi Automatic, Slambacks, etc.,some use electric resets..which are set up for G&B, or setup for Tokheim,,,,there are several different models that at first look the same but are not the same....you can't judge a computer by what wheels it has, you have to look at the PARTS on the sides.
The pic HI-Octane posted is for an electric reset....possibly G&B or Southwest....definatly NOT a Tokheim electric reset.