Williams Sound TEL040 - TeleTalker 55dB Amplified Telephone Teletalker Telephone Up to 55dB HF gain. Amplify button with amplification indicator that lights when call is amplified. Volume control boosts volume by up to 25dB. Enhance control boosts high frequency speech sounds by up to 30dB. Flashing ring indicator 95dB. High output ringer volume / tone controls. Redial button. High contrast big buttons. Dynamic Signal. Processing to improve intelligibility. Dynamic Noise. Reduction removes unwanted background line noise. Special handset speaker provides superior sound quality. Anti - feedback circuitry prevents howling (feedback) at high volume 3.5mm auxiliary jack Amplify on / off switch.