Battery Master Switch
A battery master switch (or battery isolator) is a heavy-duty switch that completely disconnects a vehicle's or system's electrical power from the battery, serving as an emergency shut-off, theft deterrent, and a way to prevent battery drain or fires by cutting all current to accessories and ignition when parked or in emergencies.

Specification
Voltage Rating: Typically 6V to 36V DC (some high-end 12-48V), matching your vehicle/system.
IP Rating (Ingress Protection): IP67/IP68 for full sealing against dust/water, IP66/IP65 for good protection (common in marine/off-road).
Key Functions & Features:
Emergency Cut-Off: Allows immediate shutdown in crashes or fires, crucial for motorsport and marine safety.
Theft Deterrent: Detachable keys prevent unauthorized use.
Prevents Drain: Stops parasitic drain from electronics when the vehicle is off.
Fire Prevention: Cuts power to prevent short circuits from causing fires.
Application: Used in cars, boats, RVs, trucks, and machinery, often near the battery for quick access.
High-Current Rated: Designed to handle the massive current needed to start an engine, not just accessories.