An apparatus for function checking of wiring matrices includes a carrier plate with a plurality of gas discharge channels formed therein. At least one selected measuring locations on a wiring matrix are ionically contacted through selected ones of the gas discharge channels, the gas discharge channels being selected by an electrode bus bar allocated to an electrode in the gas discharge channel and by controllably charging the gas discharge channels with an ionizing radiation to initiate the gas discharges. The ionizing radiation is controlled by either beam deflection or by masks.