engineering services for the design, testing and production for others, and for assistance in the design, testing and production by others, of satellite and terrestrial communication systems and networks, wireless communication terminals and modems, cellular and cordless telephones, personal communication network (PCN) handsets, cell-site communication modems, cell-site data processing and switching systems, private branch exchange (PBX) communication modems, PBX data processing and switching systems, mobile telephone switching office (MTSO) communication modems, MTSO data processing and switching systems, and component assemblies and computer programs related thereto