[ntp:questions] Re: CTS, IRIG-B, and a Sun v210

Martin Burnicki martin.burnicki at meinberg.de
Fri Apr 15 08:07:54 UTC 2005


Bjorn,

Bjorn Gabrielsson wrote:
> IRIG-Bs that I have used has been _analog_ signals - think sinus signal
> tone. RS-422 is a differential _digital_ standard - either "0" or
> "1". IRIG-B can be feed to a computer via an audio input.
> 
> I'd suggest, some more reading in the manual and hooking up an
> oscilloscope to the signal, to see what it really is.

That's not quite the truth. 

"IRIG-B" is just what many people are talking about. In fact, the "B" just
specifies the data transmission rate. 

The data signal can either be transmitted modulated on a sine carrier (what
you're referring to), or unmodulated (DC level shifted, DCLS) which is a
pure digital signal which can well be transmitted via RS-422 or other
digital signalling modes.

Normally you had to specify the IRIG code like "IRIG-Bxyz", where:

"B" stands for 100 pulses per second data rate
"x" is "0" for DC level shift or "1" for modulated carrier
"y" determines the carrier frequency, where "0" is DCLS
"z" indicates what type information is contained in the IRIG signal

Example code specifiers look like B122 (modulated) or B002 (DCLS). For more
detailed information, please see:
http://www.meinberg.de/english/info/irig.htm

I know it should be possible to decode modulated IRIG using the audio driver
(haven't tried it, though), but AFAIK there's no driver in NTP which
directly decodes the digital DCLS signal.


Best regards,

Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany



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