. . "frequency" . . "Utility_frequency#Time error correction (TEC)" . "Utility frequency#Load-frequency control" . "400 Hz" . "power line frequency" . . "50-cycle power" . "Utility frequency#400 Hz" . "commercial power frequency" . "frequency regulation" . "Utility frequency#Area control error" . "Utility frequency" . "400 Hz aircraft power" . "period of AC electric power" . "industrial-frequency" . . "frequency of the supply current" . "frequency control" . "Utility_frequency#Frequency and load" . "scheduled grid frequency" . "supply frequency" . "utility frequency" . "frequencies" . "mains frequency" . "Utility frequency#Stability" . "50\u201360 Hz" . . "line frequency" . "Load-frequency control" . "line frequency of the mains" . "mains AC power cycle" . . "\\\"25 Cycle\\\"" . "electrical network frequency" . "Power-frequency" . "switch the frequency" . "Time Error Correction" . "AC frequency" . "Utility frequency" . "power line frequencies" . "60 Hz" . "utility" . "operating frequency" . "25 Hz power" . "operate at 400 Hz" . "power-line frequency" . "50 Hz" . "line-frequency" . "power frequency" . . . "power grid frequency" . "Frequency" . "50 or 60 Hz" . "power system frequency" . "system frequency" . "frequency of the electrical system" . "grid frequency" . "25 Hz" . "power systems" . . . "power frequencies" . "the timebase for the clock was driven off a rectified version of 60 cycle AC current" . "powerline frequency" . "generator frequency" . .