Yealink Vcm36 Wireless Wifi Microphone For Yealink Systems Including The A20 And A30. Core Features: Features Optima Hd Voice Full-Duplex Technology 20-Feet (6-Meter) 360 Voice Pickup Capacitive Mute Touchpad Echo Cancellation Expansion Mic (Works With Built-In Mic) Distance Between Vc Terminal And Vcm36-W: 65-Feet (20 Meters) 2450Mah Battery Capacity, With 24-Hour Talking Time And 14-Day Standby Time.