The ADC relay driver board is simply a transistor driver for the limit relays. Each circuit has its input wired to an output of one of the various Hall-effect limit sensors. When the drivers input goes high, the transistor supplies the current to drive the associated 24V DC relay.

IMPORTANT NOTE: It is imperative that a 'kickback' diode be wired across the coil of the relay so that the back EMF does not destroy the transistor.

 

Relay Driver front view

Relay Driver rear view