<P>The basic KX-TA624 is equipped with one internal master board that supports the standard three outside lines and eight internal lines (3 x 8 configuration). But that s just the start. As needs grow, up to two additional boards can be plugged in above the first. A KX-TA62477 board adds three outside lines and eight additional inside lines (6 x 16). Or it can be added for a maximum system configuration of six outside lines and 24 internal ones [6 x 24 . </P>