Yealink VCM36 Wireless WiFi Microphone for Yealink Systems including the A20 and A30. Core Features: Features Optima HD Voice FullDuplex technology 20feet 6meter 360 voice pickup Capacitive mute touchpad Echo cancellation Expansion Mic Works with builtin mic Distance between VC Terminal and VCM36W: 65feet 20 meters 2450mAh battery capacity, with 24hour talking time and 14day standby time.