A unique, pulsed — and intrinsically safe — electrical signal is generated by the control monitor and is transmitted to the sensors via a coiled cord and optic format plug. When sensors on the transport are dry a signal is returned to the monitor. If the signal meets pre-determined characteristics the monitor goes to a “permissive” state. This “permissive” state closes a set of relay contacts which, in turn, changes the status light on the front of the 8100 series optic rack monitor from red (“non-permissive”) to green (“permissive”) signaling the terminal automation system (T.A.S.).