Yealink exp38 expansion module is designed for improving the power and flexibility of the yealink advanced ip phones sip t26p and sip t28pit features 38 fully programmable dss keys each with a dual color led connected to and controlled by the ip phone with an rj 11 cable line it creates up to 228 additional programmable extensions when 6 ext38 are daisy chained with the ip phoneyealink advanced ip phones support the functions for ip pbx such as speed dialing blfbla intercom call forward