Calibrating by NIST

Calibrating by NIST: The National Institute of Standards and Technology provides precise audio tones that can be used to calibrate electronic tuning devices.� These tones are available over the phone by calling NIST at (303)499-7111 in Colorado.� They are also available on shortwave radio.� Since most piano techs do not have access to shortwave radios, we focus on the use of the telephone service.