The Ultrasonic gap switch consists of Polyphenylene Sulphide (PPS) and is high corrosion resistant in most liquids. The gap switch is designed for high or low level alarm in different tank applications as well as pump control. However, if there is a liquid present, the signal will be transmitted across the gap and the integral electronics will switch the output circuitry to signal the presence of a liquid. It can be mounted in any position in a tank using a 3/4" or 1" thread available in BSP and NPT thread forms.