Abstract: In accordance with the present invention, defective switches of a switch array are first detected by a control and diagnostic processor by counting the transitions of actual data before and after it is transmitted through an individual switch. In addition, a generator supplies a binary test signal to idle switches, and the number of transitions of the test signal at the input of the switch is compared with the number of transitions at the switch output. If the number of transitions at the switch input and output are not the same, the switch is deemed defective, and an operator is informed of the defective switch identity. In addition, input lines to the defective switch are rerouted to a switch in a redundant or auxiliary switch array. Further, output lines coupled to the defective switch are replaced by the output lines of the redundant array.