On Fri, Jun 27, 2025 at 3:49 PM Frank Leonhardt via cctalk <[email protected]> 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
