Serene HDPhone HD40S High Definition Speech Amplified Telephone Incoming voice amplification up to 18dB Outgoing voice amplification up to 40dB DSP (Digital Sound Processing) technology eliminates virtually all distortion, echo effects and unwanted static commonly found in other ordinary amplified phones 9 photo-memory buttons for one-touch dialing 95+dB super loud ringer with adjustable ringing volume and tone controls