ESI 50 Communications Server Phone System (Refurbished)Key Features: ESI 50 includes a built in 482 port card and IVC hardware One expansion slot for another 482 card. Simply activate the IVC to add IP phones and or Esi Link licenses. Both digital and IP based Standard based design (including SIP support) ESI's Verbal User Guide Six level,100 branch automated attendant Automatic call distribution (ACD) ESI phones Desktop and cordless models Digital and IP Some models available with backlit displays