The Helios DSEL 2 is a flush-mounted rocker switch designed for controlling 2‑speed ELS fan units. It features two individual switches: one for switching the unit on and off, and the other for selecting between high and low speed settings. A second rocker switch provides an additional on/off function, allowing optional control of parallel-connected lighting. The unit operates at 239 V, 50/60 Hz, with a maximum current of 2 A (inductive load), and is rated to protection class IP30 for indoor use.