27 Jun
2025
27 Jun
'25
7:58 a.m.
On Fri, Jun 27, 2025 at 3:49 PM Frank Leonhardt via cctalk
<cctalk(a)classiccmp.org> wrote:
My memory may not be reliable, but I certainly
remember some
teleprinters could backspace a tape if you made a mistake, so I guess
they'd have had to tolerate pre-sprocketed tape. I just used them, so I
hadn't thought how it worked before now. They must have wound back
through the punch accurately so a character space could be punched a
second time. I don't remember being a special punch mechanism just for
DEL, but perhaps there was?
The Teletype model 33ASR can backspace the punch for overpunching a character.
In such machines the tape is fed by a sprocket wheel, the teeth of
which engage in the feed holes of the tape. This is positioned after
the punch die assembly. So such a punch needs a bit of help to start
it off on a new reel of unpunched tape but once it has started
punching holes properly it will carry on.
It could use tape with pre-punched feed holes, but equally it can use
unpunched tape.
-tony