Yealink SIP-T48G Administrator's Manual page 234

Microsoft Lync Edition Administrator's Guide for SIP-T2_Series and T4_Series IP Phones
2. Select the desired values from the pull-down lists of Only Accept Trusted
Certificates, Common Name Validation and CA Certificates.
3. Click Confirm to accept the change.
To upload a trusted certificate via web user interface:
1. Click on Security->Trusted Certificates.
2. Click Browse to select the certificate (*.pem, *.crt, *.cer or *.der) from your local
system.
3. Click Upload to upload the certificate.
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