[time-nuts] purpose of time of day display units

Tim Shoppa tshoppa at gmail.com
Sun Jan 22 09:44:49 EST 2017

The big clocks on the walls of the control center were largely eye-candy
for visitors, but the individual clocks at each console were continuously
used by the operators for everything (there was no computer display of
time). All important technical timing was run from dedicated sequencers but
it might be "kicked off" from IRIG-derived pulses on some occasions (in my
experience it might be spec'ed to be kicked off from IRIG but in real life
it was initiated by pushbutton).

Some control centers used a second audio channel to distribute elapsed
mission time via IRIG. That wasn't exactly my kind of control center but I
got to visit them.

In decades past I worked extensively with analog multitrack telemetry and
voice recorders that would record the IRIG analog code at same time as data
and voice. On playback we would both watch pulses and carrier from IRIG on
pen charts and scopes to derive timestamps, and we would also hook up a
standard IRIG-driven clock to the recorded IRIG audio show where we were in
the playback. We had at least one special playback station that could show
IRIG time correctly through variable speed forward and reverse driven by
the IRIG audio carrier. Much later we used minicomputers with ADC's to
digitize the data, timestamp derived from IRIG audio.

Tim N3QE

On Sun, Jan 22, 2017 at 1:31 AM, Ruslan Nabioullin <rnabioullin at gmail.com>

> Hi, looking at pictures of various time metrology equipment setups for
> best practices and inspiration, I have commonly seen time of day display
> unit(s) installed in racks containing processing or time transfer
> equipment, e.g., http://www.xyht.com/wp-content/uploads/2015/05/Powers_
> Master_Clock.jpg. All that these units do is merely display the time of
> day and sometimes the date, typically by means of seven segment LED
> displays, of the time code inputted to them (typically IRIG-B, I'm
> guessing).  Any ideas why such a unit is necessary when one can simply look
> at the time displayed by timing receivers and time code generators (and
> even some standards), and the interface of some fusor, defined in this
> context as a system which performs timing data fusion (by implementing a
> paper clock or a more primitive algorithm) and timekeeping, either by means
> of a direct shell, or via something like NTP?
> Thanks in advance,
> Ruslan
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