Stereo Batscanner and Ultrasonic Sound Detector Detect inaudible, high-frequency tones such as bat calls with the Velleman K8118: Stereo Ultrasonic Sound and Bat Detector. This DIY kit converts these inaudible noise into audible sounds waves. After assembling the kit, connect headphones and adjust the frequency to discover imperceptible sounds. Features --DIY bat scanner --Can also be used to find electrical failures in machinery, engines and electronics Specifications --Type: Heterodyne --Microphones: Electret --Frequency Range: 20 - 90 kHz --Output: 3.5 mm headphone jack --Power Consumption: 8 mA --Weight: 135 g with batteries --Dimensions: 129 x 60 x 40 mm --Power Supply: (3)