What was the frequency of the early dial tone in America? Give the answer in Hz, but you do not need to explicitly write Hz or Hertz. - Quora
60 Hz Tone 5 minutes - YouTube
60 Hz Sawtooth Tone Amplitude 1 - YouTube
Universal Bathroom Fan Motor S1200A000 Compatible with B-roan Nu-Tone 686, M686, 687, 8870 Fan Motor 3000 RPM 120V 50CFM Bathroom Vent Fan - Amazon.com
60 Hz| prueba de sonido 60 Hz- prueba de audio 60 Hz- 60 Hz Test Tone Sine Wave - YouTube