Abstract: The invention provides an automatic test system for testing and diagnosing faults in a printed circuit board carrying electronic components. The system includes an automatic test apparatus provided to receive a circuit board and produce signals indicative of faults therein which are transmitted to a repair station at which batches of faults associated with different tested boards are stored. At the repair station is also stored data enabling a display consisting of individual component parts of the circuit to be displayed and means are provided responsive to the fault indicative signals relating to a particular board for selecting an appropriate portion of the stored data to cause, under the control of a repairer a component part of the circuit wherein faults lie to be displayed in such a fashion that it usually stands out.