[GreenKeys] M28 reperfs

[Jones, Douglas W]

From: Duncan Brown <duncanancy at earthlink.net> -- Wednesday, June 4, 2025 8:45 PM

> What is strange (to me) is that they started out chadless and then went to full perf ...
> Does this imply a problem with the chadless tape?

I am only guessing, but the high-speed photoelectric paper-tape readers that were commonly used with computers starting in the 1960s were really bad at reading chadless tape.  Any time you had a TTY punching tape that was then read by a computer, you probably wanted full-perf tape.

I have or have had several photoelectric readers from the 1960s and 1970s.  None could read chadless tape.  The ones made in the 1970s tended to mechanically trivial, just a stepping motor directly driving the feed sprocket, a tape guide and LED/phototransistor read head.  Way simpler (and cheaper) than Teletype's complex mechanisms that pushed sensing fingers up through the holes in the tape.

              Doug