Patent ID: 7921889

Claim:
A power tool comprising: a base unit including a handle, a first electrical connector, and a switch positioned on the handle, the switch moveable between an on position and an off position; a motor unit configured to be releasably connected to the base unit, the motor unit including an electric motor and a second electrical connector, the electric motor including a drive member configured to enable a cutting tool to be releasably secured thereto, wherein an electrical connection is established between the first electrical connector and the second electrical connector when the motor unit is properly connected to the base unit; and a base interface circuit configured to monitor voltage levels of the second electrical connector and to generate a signal in response to detecting at least one voltage level indicating that the electrical connection exists and that the switch is in the on position; and a power control circuit configured to deliver electrical power to the electric motor in response to the signal, the power control circuit being further configured to detect that a fault condition exists when power is delivered to the electric motor while the electrical connection exists and the switch is in the off position, and to deprive the electric motor of power in response to the detection of the fault condition.