Abstract: A contact array assembly for use with a computer-controlled printed circuit oard testing apparatus includes an array of contacts into segments individually and releasably supported by supporting rods resting in a base plate. The space so created is utilized for accommodating the electronic circuitry components associated with these contact array segments and connected through plug-type connectors to a two-dimensional addressing and control logic on the base plate. These constructional units, referred to as modules or driver plates, are identical and may replace each other in any of the positions on the base plate. The invention results in a printed circuit board testing apparatus which may be designed for a very large number of contacts, but can be operated initially with a reduced amount of electronic circuitry and may be expanded later on, as desired.