DIGI-SYS ON AIR Light SD-11X5 is the most popular on air warning sign units. The unit has practically decades of trouble free life expectancy. This is due to use of Hi bright LED’s as light source. There are more than hundred specially selected LED’s used to give uniform and bright back light. diffuser system used is a high quality translucent phenolic panel. There is a strong clear back printed acrylic front sheet provide years of excellent look.ON AIR lights are available in wall mount or hanging versions. The unit is made of sturdy metal body and powder coated in Black as standard. The design includes space to accommodate loose ends of connecting wires. There are two Eye holes at the back for flush mounting it on the wall. Versions are available for 230 volts and 110 volts or automatic voltage selection.