This is a new DH-12 carwash controller, equivalent to Dilling-Harris D/H-12 P/N 77715.  Design has been updated to include heavier-duty diodes. 

This controller accepts a +24V AC or DC signal on the left side terminal strips, with the common on the right side terminal strip.  Any one or more +24V inputs will turn on the internal relay to power a 110VAC motor, pump, light, or other device.  Rated for devices up to 15 Amps. 

Typical application is for a bay carwash controller.  The carwash +24V solenoids which actuate selections such as soap, wax, etc. are hooked parallel with this controller.  If any solenoid is activated, the relay inside this unit turns on, activating a motor, pump, or other device.