Nady ALD-800 Assistive Hearing System System operates within the 72-76 MHz band designated for auditory assistance frequencies by the FCC on one of 8 factory Transmitter offers full manual controls and connections (including both mic and line level inputs), automatic level control 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