All MCE prints and manuals can be downloaded from the MCE site. As well as the triacs, the also use a universal serial bus to communitcate from I/O to processor. Hence only a couple of wires for comm from the I/O boards (CarCalls, etc) to the CPU..

It Don't mean a thing if it aint got that swing.

Cool, Free, Johnny Smith courtesy of NPR..HERE
http://www.npr.org/ramfiles/asc/asc25.smith.asx