The D-100 is an entry-level heterodyne detector employing three microphones of two types to offer maximum sensitivity across a range of frequencies. The frequency controls are backlit for ease of use and a loudspeaker is built in though headphones can be attached. This rugged unit is small enough to fit in a pocket yet sensitive enough to start you bat detecting with accuracy.
Heterodyne
Heterodyne bat detectors are great for beginners and offer immediate identification of bats in the field. You select the ultrasonic frequency range to listen to just like tuning in radio. Heterodyne detectors typically have a headphone socket and line-out socket for recording calls.

Bat Detectors

