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:

Rb OUT waveforms

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?

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    \$\begingroup\$ Probably ought to be a square wave. Might be broken, or maybe your scope isn't showing it properly. \$\endgroup\$ – JRE Sep 30 '18 at 18:33
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    \$\begingroup\$ I expect it's supposed to be a digital signal. Can you try probing a known-good 10MHz signal with our scope and the same probe/cable? That would tell us if it's the scope or the counter. Note that the waveform shown would probably still work OK as a digital output, as the edges are sharp in the 0.8 to 2V range where it really matters. \$\endgroup\$ – Jack B Sep 30 '18 at 18:36
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    \$\begingroup\$ It's possible that the digital output needs to be properly terminated (50 ohms?) before it shows a good waveform. \$\endgroup\$ – Dave Tweed Sep 30 '18 at 21:07
  • \$\begingroup\$ @ Dave Tweed Yes. That looks like a TTL output, with stronger pulldown than pullup. \$\endgroup\$ – analogsystemsrf Sep 30 '18 at 21:57
  • \$\begingroup\$ Would it be a digital zero-cross signal? It seems very well aligned despite its worn out edges. \$\endgroup\$ – K H Oct 1 '18 at 0:11

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