1 to 4 line capacity with lighted line indicators, 100 name/number phonebook directory with rapid scroll and 50 name/number caller ID history (activation required), Expandable up to 10 handsets, Volume control for handset, headset and ringer, Page, intercom and call transfer between stations , Push-to-talk intercom, 3-party conferencing (for multi-line systems), Low battery indicator, 10 speed dial and 10 intercom number locations , English/Spanish setup menu , 2.5mm headset compatible