The TR-89/B Series Transducers are rugged electroacoustic devices designed for the efficient generation of ultrasonic energy in air. They are ideally suited for a wide variety of low power, general purpose applications such as ultrasonic intrusion alarms, proximity detection devices, remote control devices, and energy management systems. The Transducers consist of a one piece housing with integral diaphragm. This provides a moisture-proof unit, suitable for both indoor and outdoor use when mounted so that the rear terminals are protected from exposure to the direct outdoor environment. The units operate at resonance on the first harmonic overtone. This affords greater efficiency (higher transmitting and receiving response) than an equivalent size device operating at its fundamental. The TR-89B Transducers can be manufactured under special order to resonate at any specified frequency between 23 kHz and 40 kHz. Massa stocks two standard versions. The TR-89/B Type 23 provides peak untuned receiving response at 23 kHz +/- 2 kHz, and the TR-89/B Type 40 provides peak untuned receiving response at 40 kHz +/- 2 kHz. The beam patterns of the transducers change at different frequencies, and greater detection range is obtained with lower frequency transducers due to the attenuation characteristics of sound in air. Thus, the TR-89/B Family offers the user a choice of transducers that have characteristics that will meet most requirements. Special frequencies, matched transmitting and receiving pairs, and other custom features are available on special order (consult factory). There are several million TR-89/B transducers in use in many different applications throughout the world.