Sarru model eTFR is a electronic ceiling fan remote regulator. It consists one controller and one remote unit. You need to install the controller at top of the fan and inside the fan canopy or plastic cap. The controller size is very small L=42mm, W=28mm, H=30mm and it can easily install. Put the batteries in remote and control your fan with remote. With remote you can turn ON or OFF the fan as well as you can regulate the fan speed in 9 different steps. It is fitted at the top and inside the fan canopy so it can be used with any type of switch board. Please note that this product is triac-based fan regulators and not inherently humming-free, although it is designed to minimize humming noise. The humming is caused by the triac's switching action and the harmonics it introduces Into the AC power, especially when the fan is running at low speeds. For its installation strictly follow the provided “Installation Guide with Troubleshooting Steps” at product detail image