I've been playing with a frequency counter (Racal 2202R) that has a built-in rubidium standard.
It has two outputs, "Rb OUT 1" and "Rb OUT 2". I could not find any documentation at all, but the waveforms look like this:
They're clearly both 10 MHz, and "Rb OUT 1" looks like a sine wave.
What might be the other output, any why does it have this peculiar shape?