Features: System operates within the 72-76 MHz band designated for auditory assistance frequencies by the FCC on one of 8 factory switchable channels -- Transmitter offers full manual controls and connections (including both mic and line level inputs) automatic level control extendible antenna and Power ON and Audio Input level LED displays. -- Any number of pocket sized ALD-800 receivers can be used with a single ALD-800 transmitter -- Receivers include mini binaural earphones providing up to 130 dB SPL for hearing assistance and feature a volume control adjust "Power ON" LED and antenna integral with earphone cord. Single standard 9V alkaline or rechargeable NiCad or NiMH battery operation.