2.5mm Mini Jack x 1

Acoustic Clarity Technology: Allows simultaneous natural conversation, the industry's best full duplex Revolutionary voice quality and clarity from up to 20 feet away Noise reduction technology automatically minimizes PC, projector, and HVAC sounds Automatic mic selection only one mic is on at a time to remove in the well sound Independent microphone, echo-cancelled channels that optimize sound Extension mics provide even greater room coverage for larger rooms Subwoofer for audio extension down to 80 Hz, which provides clearer lifelike sound Selectable, downloadable ring tones Phone Lines: 1 x Analog Phone Features: Caller ID - Bellcore type 1 Interfaces/Ports: 1 x 2-pin RJ-11, RJ-45 Buttons & Keys: 12 x Alphanumeric - Telephone Keypad, Volume Control - Up/Down, On/Off, Mute Button,... Less