Larry
They are 26 pin connectors...and the power is 74 or so volts as well. The sand works by air, not electicity and is controlled by one of the hoses on the end of the unit...Now, of course, the relays to operate the sanders valves by air are electric, as you guessed.
All functions of the trailing motors are controlled by the leader. On the rear bulkhead there is a switch that controls what end of the unit, short hood, long hood or both, that is hot. The engineer or the person setting up the power set simply needs to select the proper setting. Also, the brakes need to be cut in or cut out. Cut in is for leading, cut out is for trailing. If trailing, the automatic brake handle needs to be in handle off and the independent needs to be in full release. The electronic brakes on newer units are all set up from the computer screen on the control stand or desktop.
There is, also on the bulkhead, a selector for headlight contols. Again, if the unit is being operated as a single unit or as a trailing motor.
Denis Blake Columbus, OH