· Additional Handset only—requires an SN5127 or SN5147 Series Phone to operate· 1, 000 Name and number smart call Block directory· 50Db audio assist: temporarily increases overall volume by up to 50Db and enhances Sound frequencies that make speech easier to understand.· Big buttons, large display: oversized buttons and an easy-to-read display screen make the system Super easy and comfortable to use.· 90Db ringer volume: The extra-loud ringer makes it easy to hear incoming calls throughout your home.