The Heathkit IM-5258 Harmonic Distortion Analyzer is a vintage benchtop unit made in the USA. It is designed to analyze harmonic distortion in the frequency range of 5Hz to 100KHz. This one-of-a-kind product from the reputable brand Heathkit is a valuable tool for those in need of accurate and reliable signal analysis capabilities. Perfect for professionals and hobbyists alike, this unit offers a unique and nostalgic addition to any workspace. I put this as for parts or not working only because I don?t know how to use it. It is very clean and powers on. As a change settings the meter moves temporarily and then back to 0.