Abstract: An operational status module 11 for a vehicle security system is disclosed. A security system processor in the security system interacts with the operational status module 11 to determine if the security system should arm when an arm command is processed by the security system. The operational status module 11 has an audio or vibration sensing transducer 13 arranged to pick up a signal indicative of operation of a vehicle. The transducer 13 is connected to circuitry 15 providing a digital representation of the signal sensed by the transducer 13 which is received by a processor 21. The processor 21 will issue a control signal to cause an overriding of an arm command if the digital representation contains a signal representative of vehicle or engine vibration within a window period.