On Wed, 29 Sep 1999, Samuel A. Falvo II wrote:
> On Wed, Sep 29, 1999 at 10:10:56PM +0300, Tomi Manninen wrote:
> > NRZI (or NRZ-S) is differential. A change in level is zero, no change is
> > one.
>
> I knew this much (I've also seen it reversed: a change is a one, no change
> is zero).
Yes. And that I believe is more accurately called NRZ-M.
> But what are the sampling specifications?
Sampling specifications?
> I apologize for
> digging deep with this subject, but it seems that everyone is posting
> scattered bits and pieces of information pertaining to this, and not drawing
> from a singular, definitive source.
That's I believe because there is no such definitive source available. As
I said very little if anything is specified in the AX.25 specs when it
comes to layer 1.
The implementations we use today are more or less de facto standards. The
1200bps AFSK as we use it today was if I'm not completely mistaken meant
as a proof of concept implementation in the early days of packet radio
more than 10 years ago and never as *the* AX.25 layer 1.
Later came other layer 1 schemes like G3RUH/K9NG 9600bps, WA4DSY 56kbps,
HAPN-1 4800bps etc. These all share the HDLC framing (bit stuffing, flags
etc) but I still don't think even that is an integral part of AX.25. Tim
you said HDLC bit stuffing etc is a layer 2 issue, where does one actually
draw the line between physical layer and link layer?
> Thanks for your assistance -- it's greatly appreciated, and I really
> appreciate you folks putting up with my more or less demanding voice. :-)
:-)
--
--... Tomi Manninen / [EMAIL PROTECTED] / OH2BNS @ OH2RBI.FIN.EU ...--
