This Cortelco Single line corded business telephone is unique in the fact that in only requires telephone line power to operate. It also features flash (100/300/600 mSec) hold with Indicator redial pause mute with indicator desk/wall mountable 2.5 mm headset jack speakerphone line powered caller ID/call waiting (memory for 50 calls) wide angel adjustable LCD voice mail indication (FSK/Stutter/90V/24V) on hook pre-dial directory button (save up to 99 names & numbers) five one-touch/15 two-touch speed dial programmable flash time (100/120/300/600 mSec) handset receive volume control (8 Levels) and many more.