The Yealink YEA-EXP20 is an IP phone expansion module designed for use with T27P, T28P, T27G, and T29G series phones. With 20 phone lines, this expansion module allows businesses to expand their existing phone system capacity seamlessly. The Ethernet (RJ-45) interface ensures reliable connectivity, and since it is a free shipping item in the USA (excluding AK, HI, and PR), businesses can easily upgrade their phone system without additional costs. Made in China by Yealink, a trusted brand in the VoIP industry, this expansion module is a reliable and affordable solution for expanding phone lines.