Abstract: A multi-element piezo-electric transducer is mounted on the wall or frame of a body and is held in a predetermined position relative to the body. The support element of the transducer is subjected to an altering force by the force applying element of the transducer which applied such force when the attitude of the body changes. The altering force is transmitted to the piezo-electric element of the transducer by way of the support element. The altering force bends or otherwise deforms the piezo-electric element thereby introducing internal stresses into the piezo-electric element which thereupon generates a detectable signal. The signal is amplified and filtered to remove frequencies in the vibration range and to provide an output signal which is proportional to the extent of change in attitude of the body. The output signal of the amplifier is applied to a trigger circuit which operates an alarm.