Thank you Nigel.. frequency ratio would likely be a function of a universal
counter with 2 inputs.

There is no selector switch to select between Input A and Input B, which I
think is what you were suggesting.
That may seem odd (to me too).. that's where a manual would be handy, to see
what the actual operating procedures are like.

I forgot to mench, something that you generally include, which would be the
age of the instrument.. probably from about 1988.

--
Cheers,
WB
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"N_Cook" wrote in message
...

FR = Frequency Ratio ?
My guess , corroded switch contacts