On 2/22/11 12:12 PM, Magnus Danielson wrote:
Hi Jim!
On 02/22/2011 02:34 PM, jimlux wrote:
On 2/21/11 10:12 PM, Michael Lombardi wrote:
I'm trying to determine the first product that could automatically
decode and display a digital time code. Digital time codes were
added to WWV in 1960 and WWVB in 1965. This was before they were
added to any satellite signals, or before they were added to LF
stations in Europe, such as DCF77. Telegraphic time codes, of
course, were around much earlier.
the IRIG standaards started in the late 50s, and I'm pretty sure that
they used time code when recording on instrumentation recorders earlier
than that. You'd record a bunch of analog signals using FM on a
multitrack recorder, and because the playback speed varies and the tape
stretches, you need something to recover actual timing.
The NASA 36 bit time-code seems to pre-date both IRIG and WWV broadcast.
NASA didn't exist until 1958, but I suspect that there were folks doing
time code and it just came along for the ride.
The original WWV broadcast where in fact done in the NASA 36 bit time-code.
"STANDARD FREQUENCY AND TIME SERVICES"
http://tf.nist.gov/general/pdf/1746.pdf
I have yeat not found the NASA time code history or for that matter the
NASA standard for it.
funny, now that you mention it.. we use NASA 36 bit in places at work,
but, all my stuff uses IRIG in one form or another.
CCSDS time codes reference NASA 36 bit.. maybe a reference it's in the
back of the CCSDS standard.
the first instrumentation recorders were used in the late 40s or early
50s
there's also a famous spread spectrum system used during WW2 with
identical phono records with random noise, but I think those were sync'd
by hand.
They where synced by hand, but the turn-tables ran on synchronous motors
locked to a common frequency broadcast, so the system had an external
(common) frequency steering.
Cheers,
Magnus
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