[GreenKeys] Xerox used teletype model 35 but not ASCII

[Tom Watson]

Yes, these do exist.  They are (heavily) modified KSR/ASR 35's that work
with upper case EBCDIC.  I used one!

The ASR model had a tray of electronics below in the snap open floor
stand.  The KSR version transmitted a serial stream over a cable to send
and receive the data stream.  As mentioned, they did NOT have a control
key, as the alphabet is broken by special characters (look for an EBCDIC
table and you will understand.

There were some special keys on the keyboard as I remember, rubout (all
8 at mark, 0xff), EOM (0x05), and N/L (0x15).  There are also local LF
and local CR (as I remember).  The units used a pin-feed platen.

These were standard issue for Scientific Data Systems (later Xerox Data
Systems) on their Sigma series computers (Signa 2,3 Sigma 5,6,7,8,9).

I used it on a Sigma 5.  Once the ASR35 broke down.  I took the cables
and plugged them into another tray of electronics, and connected the
result up to an HP 2114 computer (that ran ASCII) and with the help of a
program, I had the console for the computer working again as the
mechanics were serviced.

The question remains, why a Teletype?  I suspect that it was the easiest
device.  They couldn't use (arguably better) Selectric mechanism as it
was produced by their competitor which would be bad karma.  The only
thing that might be close was a Friden Flexowriter which was being
phased out as I remember.  So, Teletype it was, modified but it worked.

Of course, one could enter control characters (the EBCDIC bell was
0x07).  I did it once by opening up the unit and forcing the two upper
bits to zero in the encoder while I typed the letter 'G' (0xC7 in
EBCDIC).  The result was a bell character being input.  On output the
units did respond to the bell character, but it wasn't used often.

Hope this enlightens people.
-- 
Tom Watson                  Generic short signature
tsw-tty at johana.com              I'm at home now