Clarity Alto Digital Extra Loud Big Button Speakerphone features TIA-4953 certified for mild, moderate and severe hearing loss. Amplifies incoming sounds up to 53 decibels and outgoing speech up to 15 decibels. Digital Clarity Power incorporates hearing aid technology for clearer call quality.Extra loud ringer volume (100 dBA). Clarity AudioCenter featuring ergonomic volume and tone control. Built-in speakerphone. Soft touch backlight keypad. Ten (10) one-touch speed dial memory buttons. ClarityLogic remote diagnostic service programs your phone at the touch of a button. Clarity VoiceAssist for talking keypad and talking Caller ID. Oversized bright visual ringer. Headset, neckloop and bedshaker ports. Battery backup lets you make calls when the power goes out. TIA-1083 compliant for hearing aid compatibility.