SIMULTANEOUSLY CHECK: Transducer resonant activity. Transducer DC leakage. Speed pickup Hall effect device. Temperature transducer thermistor. Wide Frequency Range 20 KHz to over 500 KHz. Covers most all piezoelectric marine transducers. Temperature Sensor Test Temperature of thermistor is read directly. No more guessing if the readout or transducer is bad. Speed Pickup Test Indicator flashes when the speed paddle wheel is rotated for a positive check of the speed sensor. Leakage Indicators Indicator lights if transducer fails leakage test. Resonance indicator Light Bar Eight LED's indicate transducer's activity.