[GreenKeys] FW: Flexowriter

[Jones, Douglas W]

From: Joe Clanin [macbax1 at gmail.com] -- Thursday, July 20, 2023 10:58 AM

> I'm a CS grad student experiencing a summer funding gap over in Ames and am trying to sell a few things as a result.
> Do you know anyone that may be interested in my Flexowriter FIO? (picture attached) Any leads are appreciated.

I just got the above e-mail from Joe Clanin.  I know nothing about the Flexowriter FIO other than what I found on these threads:
-- https://www.reddit.com/r/Teletype/comments/j76a1y/my_friden_flexowriter_fio/
-- https://forum.vcfed.org/index.php?threads/friden-flexowriter-fio.75486/

Joe sent me the identical photo to the one on the reddit thread, so I assume it's the same machine.  From the vcfed thread, I found this photo of the punched tape code the machine uses:
-- https://i.imgur.com/BYft7YY.png

If this machine interests you, please contact Joe at the e-mail address listed above.

The punched tape code is interesting, so I took the time to try reverse engineering it:
 87654s321
channel s is the sprocket
channels 1234 are a binary code, low bits
channel 5 is parity (so there are always an odd number of holes)
channel 67 are a binary code, high bits
channel 8 seems used only for carriage return

If I ignore the control characters, it's a monocase code closely related to IBM's 027 punched card code, where the low bits 4321 indicate a 1 out of 9 code for the numeric punches (code 0000 means punch nothing), and the high binary bits are:
   76 = 11 -- zone punch card row 12
   76 = 10 -- zone punch card row 11
   76 = 01 -- zone punch card row 10 (aka row 0)
   76 = 00 -- no zone punch
Those rules handle letters and figures correctly for tape-to-punched card codes.  Also space (punch nothing).

          Doug Jones
          jones at cs.uiowa.edu
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