Yealink SIP-T31P IP Phone - Corded/Cordless - Corded - Wall Mountable - Classic Gray - 2 x Total Line - VoIP - Caller ID - Speakerphone - 2 x Network (RJ-45) - PoE Ports - Monochrome - SIP, SIP v2, NAT, STUN, DHCP, SNTP, UDP, TCP, SRTP, TLS, IPv6, ... Protocol(s):