A container monitoring system configured to monitor access to and conditional status of a container, the system comprising: a first door controller module disposed in wireless optical communication with a controller module, the first door controller module configured to receive a first random generated code from the controller module and further configured to store the first random generated code; a second door controller module disposed in wireless optical communication with the controller module, the second door controller module configured to receive a second random generated code from the controller module and further configured to store the second random generated code; and the controller module 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, characterized in that the controller module comprises for each door controller module a plano- convex cylindrical lens and a one-dimensional position sensing photodetector, which are co-located in a mutual arrangement such that a point-source LED emission from a respective first or second door controller module, is optically transformed into a thin line orthogonal to the major axis of the one-dimensional position sensing photodetector, the thin line shifting in position along the major axis of the one-dimensional position sensing photodetector when the respective first or second door controller module, is moved with respect to the controller module, and a change in position of the thin line above a programmed threshold resulting in an alarm condition. a first door controller module disposed in wireless optical communication with a controller module, the first door controller module configured to receive a first random generated code from the controller module and further configured to store the first random generated code; a second door controller module disposed in wireless optical communication with the controller module, the second door controller module configured to receive a second random generated code from the controller module and further configured to store the second random generated code; and the controller module 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, characterized in that the controller module comprises for each door controller module a plano- convex cylindrical lens and a one-dimensional position sensing photodetector, which are co-located in a mutual arrangement such that a point-source LED emission from a respective first or second door controller module, is optically transformed into a thin line orthogonal to the major axis of the one-dimensional position sensing photodetector, the thin line shifting in position along the major axis of the one-dimensional position sensing photodetector when the respective first or second door controller module, is moved with respect to the controller module, and a change in position of the thin line above a programmed threshold resulting in an alarm condition.