Before revision: Transmitters are necessary parts of all systems that use radio: radio and television broadcasting, cell phones, wireless networks, radar, and radio navigation systems like GPS, wireless entry systems, among numerous other uses.
After revision: Transmitters are necessary parts of all systems that use radio: radio two way radios like walkie talkies, television broadcasting, cell phones, remote networks, radar, and radio navigation systems like GPS, wireless entry systems, among numerous other uses.