They have overload

Working Load 60 KG

Air is infused with the water at the pump impeller

Can be operated through ON positions with engines running (shut down engines before moving to OFF position)

Ultra Safety Systems - Ultra Pump Switches, Junior Part No. UPS-02 12V Speakers They have overloadAlarm Ready H x Dia Volts No 6 1 4" x 2 1 2" 12 These normally open pump switches operate by a magnetic reed control switch. They are self cleaning with a clog proof design. No timer delays, no electronics or mercury. They are impervious to all materials commonly found in bilges. Switch components are completely sealed against moisture. UPS 01 & UPS 02 are the same except UPS 01 series is alarm ready with an attached sensor for use with A201R optional