Question about modems

Warner Losh imp at
Thu Nov 14 23:43:36 CST 2019

On Thu, Nov 14, 2019, 10:30 PM Jim Brain via cctalk <cctalk at>

> On 11/14/2019 11:05 PM, Brent Hilpert via cctalk wrote:
> >
> > (Without having gone through the code presented in full detail, but
> thinking from root premises.)
> >
> > ASCII A = 0x41 --> 2 bits on
> > ASCII T = 0x54 --> 3 bits on
> I agree, though I believe aT,At,AT,and at are all allowed, which
> complicates things a bit aT is the bad one, where the calc for 7E1 and
> 7S1/8N1 yield the same values...

1200 baud hayes modems required the initial AT be all upper case. I can't
recall if the 2400 baud modem relaxed this, or if it was later version.

Also, AT introduced commands. +++ could be followed immediately by ATH to
hang up...

But the parity trick discussed here matches my memory as well...



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