[time-nuts] What is a Time-Nut grade Zero Crossing Circuit?

[Bob Paddock]

>  Jitter specs assume a logic
> waveform input, not a sine wave input.  Many jitter specs refer to
> pattern jitter of data, which does not apply to clocks.  Also, jitter
> increases at low frequencies in practice, even though in theory it
> should not.  Like I said, this topic is very tricky.

How exactly does zero jitter?  I understand that the logic detecting
the zero voltage point of a sine wave might not be perfect.  However
if the circuit is truly a Zero Crossing Detector, things like
the frequency and amplitude variations of the sine wave are irrelevant,
as long as the bandwidth is sufficient to the design of the detector.