An actuator assembly for selectively transmitting a heating current from a bipolar electrical generator to a surgical tool includes an actuating component with a connector for mounting the actuator assembly to the tool in a predetermined orientation. A lever arm mounted for rotation to the actuating component controls a switch that introduces current to tool electrodes when the switch is closed. A user holds the tool and the mounted actuator assembly in one hand and operates the switch with an ergonomic lever arm rotatably mounted to the actuating component. Different left- and right-hand versions of the lever arm can be used with the same actuator assembly, or the actuator assembly can accept a different lever arm configuration for use with either hand. In another version, the actuator assembly can include a guard for preventing inadvertent actuation of the switch during one-handed manipulation of the tool.
