This inline phone amplifier from Serene® can be attached to any standard phone for additional amplification up to 45dB for hard of hearing users. A rotary dial controls the volume and tone control has three discrete settings for precision. This amplifier has a headset jack for business environments and is compatible with many business headsets. Amplification stops at 35dB with a headset. Requires AC adapter (included).
Product Manual Click Here For IntelliCALL Universal In-Line Amplifier For Headsets Instructions