Core Features: W70B: Up to 20 simultaneous calls Up to 10 DECT cordless handsets Up to 10 SIP accounts Support Opus audio codec Noise Reduction System TLS and SRTP security encryption No Perception Upgrade CP935W: 4-inch multi-touch screen with 480 800 resolution Optima HD voice full duplex technology Yealink Noise Proof Technology Built-in Bluetooth 4.2 Built-in Wi-Fi (2.4GHz/5GHz 802.11a/b/g/n) Wi-Fi and DECT mode switchable (Switch via one-touch) Built-in battery Up to 20-hour talk time (in ideal conditions) Up to 167-hour standby time in DECT mode (in ideal conditions) 4 hours charging time 20-foot (6-meter) and 360-degree microphone pickup range Built-in 6-microphone array for voice pickup 5-way conference call Support to connect with a Bluetooth expansion microphone CPW25 Hybrid UC meeting