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.