Ultrasound transducers (40 kHz) as both sources and receivers.

Ultrasound: Pair of Transducers. The transducers are piezo devices for burglar detection systems. A transducer can operate as both a sound source and sound pick-up. The sensitivity of the transducer falls off sharply for frequencies + or - 40 KHz. This can be seen by trying to talk into the pickup (lower than 40 KHz). Jingling keys have harmonics which extend as high as 40 KHz. Note: Do not treat the transducers roughly. They are fragile. Use low settings for oscillator output, and high scope sensitivity. The transducer will be ruined if input power is > than 100 mw.