A machining tool, such as a forming, embossing, punching or pinching tool carries at least two tool elements at radial external faces for processing sheet metal. Differently from a conductive film like the lower electrode or the barrier conductive film, the interlayer insulating film can be formed without inheriting the orientationlevel difference from its lower layers by planarizing the surface thereof. According to the invention, the testing space is firstly evacuated and the film leak indicator is switched over to a leak search mode after the evacuation is completed. A barrier rib may be provided to partition the second electrode. Then, if the required communication rate is less than or equal to the admissible communication rate, the base station admits the request.