ESI IVX 24 Key DFP BL Display Phone (Certified Refurbished) 24 Programmable Buttons 2-Line Backlit Display (32 characters) Dedicated HELP key (combo PROG/HELP) ESLDEX, Voice Mail, Program / Help, Conference, Transfer, Hold, Flash / RDL, Record, Mute / DND, and Speaker Buttons Works With The Following Systems: ESI Communications Servers: ESI-1000 / ESI-600 / ESI-200 / ESI-100 / ESI-50 / IVX X-Class / IVX E-Class / IVX S-Class / IVX C-Class