Similar in construction to the 852, this glasses hearing aid has a built in compression circuit which means they amplify weak sounds & reduce loud sounds. This hearing aid is ideal in noisy surroundings such as one the street or crowded public places. This compression system is adjustable to satisfy individual requirements. this can be easily fitted either to the left or right ear Special Features: .3 transistor,2 diode circuitry. .Continuously variable volume control. .On / Off Switch with battery drawer .Two Position Switch Mike T.Telephone Pickup .Compression Control .Tone Control .Output - 121db .Battery lifr 120hrs.