The SL-2 is a 360 LED Strobe and/or Beacon visual indicator. LED s not only are more efficient and last longer than standard flash tubes but are also immune to shock and vibration. The LED s are internally positioned to allow a 360 viewing angle when the unit is mounted vertically and a 120 viewing angle when side mounted. The SL-2 can be user programmed to output 4 different flash patterns: Single Flash, Double Flash, Quad Flash or Flicker Flash. The unit can also be programmed as a continuous-On Beacon only, Strobe only or Beacon/Strobe allowing a lower intensity beacon to remain on and a high intensity strobe to be activated by a contact closure. 6 different brightness levels are also programmable for the Beacon and the Strobe. All programming is stored in non-volatile memory so you won t lose the programming when the unit is powered down, allowing you to program units prior to installation. The SL-2 is designed for indoor applications and comes standard with a Blue shatter resistant polycarbonate lens. Optional Red, Amber and Clear lenses are sold separately (go to www.vikingelectronics.com and click on spare parts). Unit surface mounts to wall, post, panel, 4 electrical box or wet location electrical box round lamp holder cover. The model SL-2-EWP adds Enhanced Weather Protection (EWP) for outdoor installations where the unit is exposed to precipitation or condensation. EWP products feature foam rubber gaskets and boots, sealed connections, gel-filled butt connectors, as well as urethane or thermal plastic potted circuit boards with internally sealed, field-adjustable trim pots and DIP switches for easy on-site programming. For more information, see DOD# 859.