[GreenKeys] M28 Line relay mounting assembly wanted for LESU

[Bill Horne]

"W2HX" <w2hx at w2hx.com> said:

> Wasn't ebcidic a 12-bit code? 

AHA! Finally! Something I know about!

If Teletype ever made a machine that spoke an "IBM" code, it was
almost certainly the "EBCD" code, not "EBCDIC". I know this because I
had to learn about EBCD the hard way, a long time ago.

When I was in college, I bought an Anderson-Jacobson 841 terminal from
the M.I.T. surplus market. I needed a printer, back when computer
printers cost $500 at least (back when Five Hundred, etc.), and this
cost Forty dollars. 

It was, basically, an IBM Selectric typewriter, with some added RTL
(correct) logic and solenoids on the bottom of the Selectric mechanism
which drove the printer from the RTL logic. It also contained a modem,
in addition to an RS-232 25-Pin connector for local I/O.

The machine used a code called "EBCD", which is a SIX bit code, having
(of course) 64 possible combinations. It has "Shift" and "Unshift"
codes, just like Baudot, so the machine had 126 code combinations. Of
course, "EBCD" and "EBCDIC" are two different codes, and although they
share a common ancestry, they're not compatible.

The machine operated at 137.5 baud, which turned out to be something I
could set in the 8250 UART on my Heath H-89, and it used "Odd" parity,
which caused me no end of confusion until I figured out that the 8250
had a separate setting for parity which was not related to the word
length setting. Long story short, I got it going, after I put an ASCII
to EBCD lookup table inside the CP/M printer driver. I was the only
guy in my professor's group who had justified right margins on my
papers, and I think that made a big difference in my grades. :-)

And, after all that, I found out that Tymnet would not only do the
speed and code conversions automatically, but that I could connect to
Prodigy and receive emails on it. Back then, that was impressive
stuff. ;-)

More details are at 
http://www.hartetechnologies.com/manuals/Unclassified/Anderson_Jacobsen_AJ-841_Selectric_Terminal_Ma.PDF

HTH. Ask again, anytime. 

Bill, W1AC