FIG. 1 is a left side, front and top perspective view from above of a central casing unit for associated telephone sets of an intercommunication system showing my new design;

FIG. 2 is a plan view of the top thereof, the bottom being plain and unadorned;

FIG. 3 is a front end elevational view thereof;

FIG. 4 is a rear end elevational view thereof; and

FIG. 5 is a left side elevational view, the side opposite being a mirror image thereof.