28 Jan
2014
28 Jan
'14
6:03 p.m.
On Tue, Jan 28, 2014 at 7:40 PM, Paul Koning <paulkoning at comcast.net> wrote:
I don't remember ever seeing a Model 33 with parity. And weren't
telegrams sent in 5 level code? If not at the end, then surely before
ASCII appeared. And of course before either, there was Morse code, which
doesn't come with parity either.
All parity can do is convert garbled characters into missing characters.
Neither is good. Telegraph operators probably relied on having good
signal quality, ensuring adequate bit error rate values, at which point
parity is not particularly needed. And with Morse, you're probably relying
on skilled operators -- ECC performed by trained brain cells.
Wikipedia seems to indicate that the Model 33 ASR sent 7-bit ASCII with
even parity. I've found that in many of the programs on my PDP-8/E, even
parity is required, which I presume stems from the Model 33 ASR days.
Kyle