Filters for radio interference suppression, namely, low pass filters, high pass filters, band pass filters, channel filters, band rejection filters; radio frequency equalizers; multiplexers; signal splitters for electronic apparatus; FM modulators; radio frequency converters; converters, electric; frequency multipliers; radio frequency detectors; amplifiers; pre-amplifiers; electric couplings; semiconductor devices; receivers of microwave electronic signals; RF tuning devices: testing and measuring equipment for use in testing the performance and efficacy of radio and microwave frequency telecommunications equipment