Transport refrigeration door status sensing device for shipping container rear door and evaporator door has controller that selectively generates alarm based on third signal from receiver

摘要

An emitter attached to a container (10) transmits a first wireless signal e.g. polarized laser beam toward a door (14). A reflector (24) coupled to the door and aligned with the emitter senses the first wireless signal and generates a second wireless signal that is received by a received attached to the container. The receiver generates a third signal indicating the condition of the door. A controller selectively generates an alarm if the third signal indicates that the door is in the open condition.