Are there certificates required for VoIP?

The BT110 device uses device specific key and certificate for HTTPS Provisioning and TLS-based SIP signaling.  For the server root certificates, the BT110 allows specific root certificates for the provisioning server and the Proxy server to be uploaded to the BT110 device. If these specific certificates are present, the BT110 uses these specific servers in the authentication process. If these specific certificates are absent, then, the BT110 searches root CA certificates in the Linux default root certificate bundle. The BT110 device fetches the Linux default root certificate bundle during power-up, and checks for updates once per day. To upload or delete these specific  root CA certificates, navigate to System > Certificate & Keys.