Thanks Jos, Tony and Rod - you've neatly highlighted why I found the screen printer so curious and fascinating, an oddball feature in the terminal world and seemingly a simple mechanism to render the screen.
If anyone with access to one has the interest and time I'd appreciate pictures and any additional detail of how it works; if you can make one print, pictures of what it can produce would be great too. It has always struck me that VT52 screen printer has never been fully described or experienced, and I don't know of any other display devices that had it built-in (I'm ignoring later devices like the Sony screen-printers that rendered to thermal paper etc.) Some years ago I expended some effort and scoured the internet for a picture of the output and I vaguely recall I found a single image, but it appears I filed it too well and now can't find it.
