Lock mechansim using valve to lock piston

A system for sensing the security of a container includes a housing, at least two lock members coupled to the housing, the lock members configured to couple to first and second portions of the container to lock at least one container door in a closed position, a signal generator configured to generate a first signal and couple the first signal to the first portion of the container, the generated first signal having a known profile, and a lock controller configured to cause the signal generator to generate the first signal upon occurrence of a trigger event. The system further includes a signal detector configured to receive a second signal, the second signal resulting from the first signal, and a signal analyzer configured to analyze the second signal to determine a profile of the second signal, retrieve stored data representing a signal profile indicative of the lock mechanism being coupled to the first and second portions of the container, compare the profile of the second signal to the stored signal profile, and determine that a relationship between the lock mechanism and the container has changed based on the comparison.