[time-nuts] Reference input on HP counters

[Jerry Hancock]

I’m being a little lazy as I can check the schematics, but in the general case, do HP counters, frequency generators, etc, switch to the external reference when one is available or discipline the internal oscillator?  Are there brands of test equipment that generally discipline vs switch?

Third question, again generally, when you discipline an oscillator, what impact does this have on the oscillator's phase noise?  I assume this third question depends on the discipline loop (if I’m using the correct term).

Thanks