Terrestrial and satellite radio service providers transmit radio programming via the open airwaves, cable networks, and communications satellites. They differ in terms of cost, coverage and capabilities. Some terrestrial and satellite radio service providers offer nationwide or regional coverage. Others serve a more limited geographic area such as a state, province, city, or county. Terrestrial radio service provides use land-based antennas and antenna systems for two-way radios, cellular telephones, personal communication systems (PCS), and microwave applications. A terrestrial radio infrastructure uses telecommunications hardware such as filters, amplifiers, duplexers, combiners, multi-couplers, power supplies, surge suppressors, and waveguides. Satellite radio service providers use one or more communications satellites and repeaters. Typically, these repeaters are located in urban areas where tall buildings or tunnels may interfere with line of sight (LOS) transmissions.