The E-10A and E-20B are telephone line powered speaker phones designed to provide two way hands free communication. Both function identically, but are available in two different housings to better suit the application. When the Call button is pressed, the E-10A or E-20B will come off-hook and will remain off-hook until a CPC signal is detected, the programmed timeout has elapsed, a busy signal is detected, or the call goes silent, making the unit automatically disconnect. _DELETE_