[ntp:questions] Meinberg DCF77 C51 with Linux 2.6

Uwe Klein uwe_klein_habertwedt at t-online.de
Mon Feb 12 08:27:27 UTC 2007

David Woolley wrote:
> Message-ID: <7e94a4-6cf.ln1 at robert.houseofmax.de>
> From: Uwe Klein <uwe_klein_habertwedt at t-online.de>
>>the same happened if the currentloop in rs422 was broken
> Although the relevant parts of the article seem OK, rs422 is not current
> loop.  I think current loop is so old that it pre-dates current loop.
> RS422 is bipolar balanced.  Current loop is unipolar, and likely to be
> unbalanced.
You are right there: RS422 is a +-5V shift symmetric driver that works on
an end terminated line of fixed impedance. ( usually point to point )
The receiver evaluates the voltage across the wire pair.
RS485 is the same but bidirectional and multi station. The transmission
line is terminated on both ends, the line accomodates a limited number
of taps.
Currentloop is what forex old ttys are connected, essentially a telephone line.
> I think RS422 receivers are biassed in the same way as RS232 ones so that
> a physical line break doesn't result in a spacing condition, and therefore
> a break condition detection.  (I suspect this is why RS232 data and control
> lines have opposite senses, so that disconnected goes to control false, but
> to data marking.
I would have to read up on my old datasheets for the SN75xxx thingies ;-)
> Incidentally, your copy of Mozilla seems to have been configured not to
> request German language responses; is that what you intended?
never decided this, it's the default with using Mozilla with the default (en)
language settings ;-)


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