Dialed in to 9 -[ HMM ]-

Frequency control on an old (late-1960s/early-'70s) Hewlett-Packard 3300A function generator, a device used to generate electrical waveforms, such as test tones.

 

Depending on the position of the range switch, this setting would yield frequencies of either 9/100, 9/10, 9, 90, 900, 9,000, or 90,000 hertz.

Done