Method and apparatus for functional expansion through predefined signal interfaces

A method and apparatus for increasing system functionality through a predefined interface is disclosed. Signal lines which are not used or which are not used in certain modes are connected to an interconnection device instead of being connected to an interface wherein the output of the interconnection device is connected to the interface where such lines would have been connected. The interconnection device also has a set of inputs for receiving signals from a device providing the desired functionality. A controller chooses between the two sets of inputs to control what signal lines are connected to the predefined interface. Accordingly, during certain modes of operation, the added functionality from a device whose output is being switched into the interface can be supported. In one embodiment, speaker phone capability is provided for even though the predefined PCMCIA interface does not support such capability. The disclosed design continues to maintain capability with all systems adapted to be used with such predefined interface.