Abstract: A programmable cable adaptor in accordance with the present invention includes a housing containing an internal circuit board having a plurality of conductive traces, an input connector with multiple pins or pin-receiving sockets, and an output connector with multiple pins or pin-receiving sockets. On the circuit board, there is a card edge receptacle with key-contacting pins electrically connected to the conductive traces which in turn electrically couple the receptacle pins to the input connector and/or the output connector. The key-contacting pins of the card edge receptacle are arrayed along at least one side of an elongated aperture adapted to receive an adaptor programming key generally referred to as a card edge key The "key" is typically a small printed circuit board with conductive tabs on at least one side thereof with each tab being electrically connected to at least one other tab on the key with conductive traces.