The yealink exp39 lcd expansion module has been designed to improve the power and flexibility of the advanced yealink ip phones it features a 160x320 graphic lcd and 20 physical keys each with a dual color led these show very clearly which function had been selected and make operation very easy what is more you can add 20 additional keys via a page switch bringing the number of programmable keys up to 40 each programmable key supports functions that include speed dialing plus blfb