Abstract: A container monitoring system can generally comprise a first door controller, a second door controller, and a controller module. The first door controller module can be disposed in communication with a controller module. The first door controller module can be configured to receive a first random generated code from the controller module and further configured to store the first random generated code. The second door controller module can be disposed in communication with the controller module. The second door controller module can be configured to receive a second random generated code from the controller module and further configured to store the second random generated code. The controller module can be configured to separately interrogate the first door controller and the second door controller and configured to establish an alarm condition based on one or more signals received from the first door controller and the second door controller.

Abstract: A container monitoring system can generally comprise a first door controller, a second door controller, and a controller module. The first door controller module can be disposed in communication with a controller module. The first door controller module can be configured to receive a first random generated code from the controller module and further configured to store the first random generated code. The second door controller module can be disposed in communication with the controller module. The second door controller module can be configured to receive a second random generated code from the controller module and further configured to store the second random generated code. The controller module can be configured to separately interrogate the first door controller and the second door controller and configured to establish an alarm condition based on one or more signals received from the first door controller and the second door controller.

Abstract: Enclosure door status may be detected. Light may be transmitted from a first component. The light may be received at a second component when a door is in a substantially closed position. The door may be mounted on a structure wherein an angle of incidence between the light transmitted from the first component and the second component increases proportionally to an angle of incidence between the door and the structure. The door may be determined to be in an open position when a light intensity received at the second component is less than a predetermined light intensity value that corresponds to a predetermined angle of incidence between the door and the structure. The first component may comprise a low divergence light emitting diode (LED) transmitter that may be configured to transmit light at a wavelength of approximately 950 nm. The second component may comprise a low profile silicon photodiode.