A linear light-emitting diode (LED)-based solid-state universal lamp using a frequency sensing and control mechanism operates normally with both an electronic ballast and the AC mains. The frequency sensing and control mechanism automatically detects voltage types associated with output voltages from the ballast and the AC mains in a single-ended or a double-ended lamp fixture and makes proper management so that the universal lamp works for either case and in either fixture without operational uncertainty. When two shock protection switches are used in two lamp bases, the universal lamp fully protects a person from possible electric shock during initial installation and re-lamping.