Hi,
     This moc was originally built circa 1999.  It has been revised three times since then.
The current version utilizes two separate pressurized circuits.  Each circuit has one piston and one switch.  Circuit X’s piston actuates Circuit Y’s switch and vice versa.
For Info, Questions, or comments:   http://news.lugnet.com/technic/?n=9290  or daniel_family2000@yahoo.com
Thanks Chris