The Hamilton Electronics VHF Assistive Listening System eliminates hearing barriers by delivering superb sound quality that ensures ADA compliance at any large venue. All you need is one transmitter and it can serve an unlimited number of receivers within the ALS-600's 300 foot radius. The ALS-600 has separate volume and power controls, 109 mW max into 16 ohms Audio Output, 3.5mm mono mini jack for earphones and also includes Mini binaural earbuds. Single transmitter serves unlimited receivers. Expandable. Operating Range Up to 300 feet line-of-sight. Ideal for schools and churches. Operates with 9V Alkaline batteries.