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.