Microsoft offers two licenses for participants in Teams meetings and calls on their Teams room video conference system.

Microsoft Teams Meeting Room Pro offers an enhanced in-room meeting experience with features such as intelligent audio and video, front-row and large libraries, and dual-screen support. In addition, the Teams Meeting Room Pro license also offers advanced management features such as remote device management, conditional access policies, and detailed device analysis.

The Microsoft Teams Meeting Room Basic Edition provides the core meeting experience for organizations that purchase a certified Microsoft Teams Meeting Room system at no additional cost. The Teams Meeting Room Basic license includes planning, joining meetings, content sharing, and collaborative whiteboards, as well as fundamental security and readily available management features.

Desktop
Your calendar in Teams is connected to your Exchange calendar. In other words, when you schedule a meeting in Outlook, it'll show up in Teams, and vice versa.
Every meeting scheduled in Teams is automatically made into an online meeting.
1. Select Schedule a meeting button in a chat (below the box where you type a new message) to book a Teams meeting with the people in the chat.
2. Go to the Calendar Meetings button on the left side of the app and select new meeting in the top right corner.
3. Select a range of times in the calendar. A scheduling form will pop open.
The scheduling form is where you'll give your meeting a title, invite people, and add meeting details. Use the Scheduling Assistant to find a time that works for everyone.
For further details, please go to https://support.yealink.com/en/portal/knowledge/show?id=60d47355076300004a00703d

A20 can support 3 types of microphones,
（1）VCM34——1
（2）VCM38——1
（3）CPW90——1 pair（2 pieces）
Note: The built-in microphone is disabled when using an external microphone, and the A20 cannot be used with an external speaker.