Hearing Aid-Compatible Handset ADA/HAC compatible.;Handset Jack - Modular jack to connect coiled handset cord from handset to telephone.;Ringer Volume - Adjusts ringer volume to LOW or HI. Located on the bottom of the phone.;Data Port - Provides access to the telephone line for optional connection of modem, fax, or answering machine.;Volume Switch - Volume control switch on the handset steps through the three available handset volume levels Normal to Medium to High