A process is provided for the selective metallization of 3D structures, particularly for the selective gold-plating of 3D contact structures on wafers, such as contact bumps, which are electrically connected to a bond pad on the wafer via a three-dimensional, mechanically flexible structure in the form of a redistribution layer, for subsequent electrical connection to a carrier element, e. A signaling message processing and routing node transmits and receives short message service data packets via a communications network. By evaluating a relative signal between the test injections within one work cycle in the two cylinders, an intrinsic dependence of the drive train of the quantity of fuel signal is compensated. If the case is opened the connector no longer provides an electrical connection between the first and the second circuit boards, triggering a tamper detection circuit. The instrument and method also support parametric testing of transceivers used for WiFi positioning and, optionally, GNSS positioning by the same mobile device used for WiFi positioning.