Abstract: Disclosed is a wholly electronic system for either testing or changing the state of a bi-stable circuit element such as a crosspoint of a switching matrix under the control of a central processor (CPU). A maximum of 256 groups of 128 points may either have the condition changed (driven) or the condition read (scan) by the apparatus shown under the control of a processor such as a 16-bit CPU. Interfacing between the CPU and the switching matrix is a bi-directional multiplex gating and decoding tree network having at its outer extremities the points. Each point is represented by an address comprised of bits representing word, basket, group and level. By addressing a point and then providing a control indication as to whether the condition of a point is to be read or whether the condition of a point or group of points is to be changed, the points can be readily scanned or driven according to instructions received from the CPU through a logic unit or controller.