Yealink T55A, IP Phone, Gray, Wired handset, In-band, Out-of band, SIP info, 4.3", 480 x 272 pixels Yealink T55A. Product type: IP Phone, Product color: Gray, Handset type: Wired handset. Dual-Tone Multi-Frequency (DTMF) modes: In-band, Out-of band, SIP info. Display diagonal: 4.3", Display resolution: 480 x 272 pixels, Touchscreen type: Capacitive. Voice codecs: G.711a, G.722, G.723.1, G.726, G.729A, G.729B, iLBC. Ethernet LAN interface type: Gigabit Ethernet, Supported network protocols: IPv4/IPv6, Security algorithms: HTTPS, MD5, SIPS, SRTP