3 different models for a complete offer: Premium lil entry model Premium Ei] middle range model Premium ER] top of the line Strong points + One-touch and two-touch memory keys capacity (all models] and Phone book capacity (Premium 300] » Features activation with less signal {for speaker microphone mute headset key ringer message waiting key} + 8 ringer melody choice + All models fully line powered [no AC, no battery required) » PROMOTE memory backup Ino unfortunate file erasure] + Handset/headset listening