① Volume＋
② Volume－
③ Anwser call*
④ End call*
（
*Answer call and End call button should match with the specific VC software.）
⑤ Mute
⑥ POE output (for daisy-chain the next A20)
⑦ USB Type-C
⑧ POE input (for daisy-chain with the previous A20 or C30R)
⑩ Reset button
⑨ DC power port
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5
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3
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