Gettin' no love here I see. (Caught your question in the other E/S thread.) I have the sinking institute and can tell you what it physically does(when it sinks, what switches trigger to send it back up, etc) but not electronically. A little over my head there. If that is helpful I can get you some video.

I went looking for my old notes, but I couldn't find them. I considered guessing, but it's been a long time, so I ran a test, and I would definitely have guessed wrong.

The original design for the building was to have it collapse 1/3rd the way on the first ball lock, 2/3rds the way on the second ball lock, and then all the way down for the third ball lock. The building stays down until multiball is over, and will then come back up.

If you look up Earthshaker on the IPDB, you can download the pages from the manual that refer to the Building Assembly, as well as the prototype ROMs which include the proper motor and switch labels, and a "Building Test" that you might find useful.

The drawings describe a dual opto board, but does not picture the plastic wheel with "walls" that block those optos at various points during the building movement.

For reference, the motor is an 11rpm motor, similar to the ones used for pretty much any System 11 game with a moving target bank (like BK2K). I think Cyclone also uses the same motor for the Ferris Wheel.

Anyway, here are the switch combinations as reported during the Switch Test:

Building Up: Only Switch 26 is closed
Building 1/3 down: Both Switches 25 and 26 are open
Building 2/3 down: Only Switch 25 is closed
Building Down: Both Switches 25 and 26 are closed

The whole "collapsing by thirds" idea isn't implemented in any version of the software that I am aware of. However, if you don't follow the proper switch combinations, the building motor will turn off.

Good luck, and let me know if you have further questions.

Bill Ung -- UFO Pinball