A signal generated responsive to a magnetic field in a magnetic circuit is decomposed into first and second filtered signals, wherein, at at least one first frequency, a magnitude of a component of the first filtered signal is greater than that of the second filtered signal, and at at least one second frequency greater than the at least one first frequency, a magnitude of a component of the second filtered signal is greater than that of the first filtered signal. A condition of a magnetic circuit is sensed responsive to the first and second filtered signals. In one embodiment, actuation of a safety restraint actuator of a vehicle is controlled responsive to the sensed condition of the magnetic circuit that includes a portion of the vehicle susceptible to a crash. A deployment threshold is adjusted responsive to a door opening state.