This AC motor speed controller is for brushed AC motors only. It changes output voltage from 0-120V to adjust motor speed, light brightness, or heater temperature. The LED display shows the current voltage setting. The resettable 15A circuit breaker automatically interrupts power during overload – no fuse replacement needed. Size: 5.5 x 2.4 x 2.25 inches, with a 3-ft power cord and a belt clip. Standard US socket is designed for grounded 3-prong plugs (Type A & B outlets). Works with: Inline duct fans, exhaust fans, routers, drills, angle grinders, polishing machines, incandescent lamps, and resistance heaters. Note: Minimum recommended load: 60W. Some motors may produce a humming sound at low speeds – this is a common characteristic of this type of regulator. If adjustment range appears narrow (only on/off), the connected load may be too small; try a load of at least 60W. Troubleshooting: If the controller does not adjust speed, check that the internal potentiometer connector is fully seated (transportation can loosen it). Do not use with: Brushless motors, DC motors, induction motors, capacitor-run motors, or any device with electronic control boards (e.g. smart appliances, pumps, microwaves, LED lights). Also not for devices with capacitors or electronic components inside. Confirm your device has carbon brushes before purchasing.