OK/Red Letter Game - OK/Red Letter Unit
On earlier games, the ok/red letter unit stepped up once every time the green score unit stepped up, and it essentially acted as a bunch of extra wipers/rivets that could have been on the green score unit if there was room.
On the new design, the ok/red letter unit stays reset and does nothing until an ok/red letter game is won and it's time to reset the machine and configure it to the proper score/feature levels.
On our example for an "O" level red letter win, we previously showed that the pulse stream is connected to wiper D (green highlight) on the ok unit disc. In the unit reset position, this first pulse goes nowhere because the rivet under the wiper finger is not connected to anything. Recall, however, that the pulse is also stepping up this unit, so wiper D rotates one rivet counter-clockwise on the diagram as well.
Since the "O" level is not pushing scores up very high, not all the 24 positions on the unit are needed, so the first three steps of the unit continues to position wiper D on disconnected rivets. On the fourth step, however, wiper D connects to a purple rivet that is tied to wire #78-15.
Bally nicely labelled the interesting rivets on the diagram, and you can see wire #78-15 is connected to the selection feature unit step-up coil. As the ok unit is stepping from position 4 to 5, the selection feature unit steps up once. Wiper D rotates another rivet and again lands on a purple rivet, so the next pulse also steps up the selection feature unit. Eventually the selection feature unit steps up four times, then wiper D starts stepping up the red score unit.
This process continues through the yellow score unit, magic screen feature unit, and finally trips the red supersection trip relay via wire #90-12.
This all works because a stepper unit is mechanically slow. There is a race condition since the same pulse needs to step up the ok/red letter unit and also power another unit step-up coil or trip relay coil. However, powering a coil is lots faster than ratcheting a wiper around, so everything works as desired.
Note that different wipers on the unit may do things in different order, and may skip enabling features entirely if the red letter level isn't supposed to award them. For example, the minimum "B" level does not enable rollovers or supersections, so no rivets under wiper A connect to wires #78-15, #90-12 or #20-7.
