The ELK-100 Siren Driver is a great choice for residential and commercial security installations. It is extremely loud and draws less current than most siren drivers. Our exclusive MilliMiser option allows further reduction of current draw for controls that have limited alarm or auxiliary output power. The ELK-100 has two inputs, Yelp & Steady, and comes pre-wired for ease of installation. The Yelp input has our unique ComboTrigger feature, especially designed for controls that have a single alarm output with a pulsing option for fire or burglary. When pulsed, this channel produces a distinctive third sound pattern.