Which device relies on a stable low-frequency oscillator, with harmonic output, to facilitate the frequency calibration of receiver dial settings?

A frequency-marker generator uses a highly stable, low-frequency crystal oscillator (such as 100 kHz) designed to produce a waveform that is rich in harmonics. These harmonics appear at regular, predictable intervals across the radio frequency spectrum. Because these signals act as distinct "markers" at exact multiples of the fundamental frequency, operators historically used them to calibrate analog receiver dials and ensure they were tuned to the correct frequency band edges. While a "frequency counter" measures an input signal and a "signal generator" outputs a specific test tone, neither is specifically built to provide an array of simultaneous calibration markers. "Harmonic calibrator" is simply a plausible-sounding distractor.