On Feb 22, 2011, at 11:53 PM, jimlux wrote: > 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.
Thus the rather interesting start time for some of the time codes of January 1, 1958 with a roll over modulo 256 or what ever ... > >> >> 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 >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
