Abstract: A high current, light weight, thermally stable, bidirectional semiconductor switch module in an electrical system uses MOSFET technology in a back-to-back parallel architecture. The device comprises a controller which permits it to operate in high electrical noise environments. The device is further controlled to operate in either or both directions based on external events such as voltage changes associated with the electrical system and with vehicle operating conditions. The device operates at currents typically from a few amperes to 1000 amperes and may be used as a circuit breaker, over voltage switch, isolation switch, transient protection switch, and voltage converter. The device functions to replace the solenoids and relays associated with starter motors in a vehicle electrical system.