Abstract: An alarm is provided for a container including an enclosure, a door, a door latch, and an actuator to open the latch. The alarm includes a switch, a circuit, and an output. The actuator actuates the switch when it opens the latch. In turn, the circuit senses the position of the switch and drives the output if the latch is open. Additionally, the alarm may include a power supply that powers the circuit via the switch when the latch is open. The alarm may also include a guide that prevents relative movement in one direction between the actuator and the switch. A lock switch may also be connected in series with the actuator switch so that the circuit drives the output only when the latch is open and the lock is locked. Additionally, a housing fitted to a lip of the enclosure may contain the circuit.