The liquid level switches specified are intended for use in shipboard sewage Marine Sanitation Devices (MSD) and Graywater Collection and Transfer (GWCT) systems aboard surface ships or craft. An MSD is any equipment onboard a ship or craft designed to receive and treat sewage (blackwater) to a level acceptable for overboard discharge, or which receives and retains sewage onboard for later discharge ashore or in waters where discharge is permissible. The U.S. Navy uses the term MSD to also refer to equipment that receives and treats a combined sewage and graywater waste stream. The switches are used in conjunction with pump control and alarm circuitry to govern pump operation and activate tank high- and low- level alarms installed in MSDs and GWCT systems.