A method and an apparatus for upgrading an existing service outlet (e.g. LAN, telephone, power or CATV outlet) in a house by adding functionality thereto. The functionality is added by an add-on module, connected electrically and secured mechanically to the existing outlet. Several attachment devices are exampled, including surface attachment, side clamping, snap locking, strap securing and fastening screws. The add-on module may include a service connector for retaining the basic existing outlet function. The module may be attached in a permanent way or by using a detachable solution.