Yealink T42S offers 12 VoIP lines with HD audio via G.722/G.711, dual Gigabit PoE RJ45 ports, a 2.7‑inch monochrome LCD, one USB 2.0 port, six programmable keys, voicemail, caller ID, call transfer and conference support, full duplex, QoS, IPv6 ready, wall‑mountable with digital volume control and a 1000‑entry address book.