Abstract: A fail-safe varistor includes either a fail-short or a fail-open device. Both devices include a fusible, electrically conductive material that melts before the varistor fails due to overvoltage. In the fail-open device, the fusible, electrically conductive material joins separated portions of the leads. The material also may join at least one of the leads directly to a ceramic disk of the varistor. Upon reaching the predetermined temperature, the varistor melts causing a circuit including the varistor to open. In the fail-short device, the material melts creating a short between the leads. This short causes a fuse or a breaker to open the circuit.

Abstract: A device for suppressing transient surges in electrical power available from an electrical outlet is disclosed. The device is adapted for mounting on a back side portion of the electrical outlet. Surge protection components, such as planar varistors are disposed within an insulative housing block which forms the body of the device, and the device is physically mounted and electrically connected to the electrical outlet by mounting apparatus such as stiff metal leads.