1.Normally open (NO, most commonly used) Non-magnetic disconnection, magnetic conduction; door magnetic sensor, liquid level floating ball, limit detection main flow. 2.Normally closed (NC) Non-magnetic conduction, magnetic disconnection; a few power-off protection and liquid level lower limit alarm are used. 3.Conversion type (SPDT, 1 open and 1 closed) Three pins, normally closed without magnetic connection, switched to normally open with magnetic connection; small signal switching, gear detection. Differentiated by withstand voltage/power Small signal reed switch: within 0.5A, below 100V, weak current signal detection High voltage reed switch: it can reach 1 kV ~ 10kV, and it can be used with high voltage relay, insulation detection and withstand voltage equipment (the high voltage circuit you asked before is commonly used) High-current dry reed relay: dry reed tube + excitation coil are integrated to form a dry reed relay