Abstract: Apparatus for selectively interconnecting different pieces of audio electrical equipment, such as an amplifier and a tuner, for the purpose of demonstrating the same to a potential purchaser. Units to be demonstrated are connected to different address-assigned ports in the apparatus, and a keyboard is operated to address the particular ports for the units desired to be connected. The apparatus includes an electronic memory which stores the addresses of the addressed ports, and which then effects a connection between such ports.