Polycom VVX 501 Corded Business Media Phone System - 12 Line PoE - 2200-48500-001 - AC Adapter Included - Replaces VVX 500 Desktop VoIP Conference Phone - High Definition Audio Technology -Voice Over Internet Protocol (VoIP) - Session Initiation Protocol (SIP) - HTML5 Browser 12-Line Operation -Caller ID -Acoustic Clarity Technology -Hearing Aid Compatible Speakerphone - Dual-Port Gigabit Ethernet Switch -ADA Volume Control Compliant 3-Way Conferencing - USB Port - Call Forwarding - Remote Missed Call Notification Adjustable Ringer/Volume Control - Call Transfer - One-Touch Speed Dial - One-Touch Redial