The SmartGate system generates an invisible, non-contact field precisely where it is needed: moving with, and preceding, a gate arm or door to sense potential contact before it happens. The invisible field can "sense" conductive objects, such as people or vehicles. Packaged in a compact, rugged housing, the SmartGate system can easily be installed into a new or existing gate in about one hour. The system signals the gate operator to stop or stop and reverse the motion of the closing gate arm in the event a person or vehicle is sensed in the danger zone of the moving gate arm.