SIP Protocol: SIP 2.0 (RFC3261). DTMF: RFC 2833 SIP INFO. Support: 2 Way SIP Account. Support: SIP UDP TCP TLS. WIFI: IEE802.11b g n Support. High Definition Calling: Desk phone supports for Volte HD calling, no need to have a microphone close to your ear to enjoy high definition sound quality.
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