Serene Innovations Universal Handset And Headset Amplifier Siua50

Amplifies incoming voices up to 170 times (45+ dB), so you hear every word with unmatched clarity. Selectable digital tone enhancement allows you to boost and enrich the speech fequencies you can't hear well, making difficult to hear words intelligible again. Automatic gain control optimizes sound level for superior listening comfort. Easy headset/handset selection button for extra convenience. Latest digital sound processing technology eliminates virtually all distortion, echo effects and unwanted static commonly found in other ordinary amplifiers. Works with virtually all business telephones and headsets; it connects between phone's handset/headset and base. AC adapter included, battery (9V) optional.