cj7hawk
Veteran Member
The 4 pin does certainly point to a hookup to a serial terminal. I've not seen a jack with the latch on the side, but perhaps someone recognizes it.
It would be useful to get a high-resolution photo of the whole board to see what's feeding that jack.
It's a British Telecom socket. Like RJ, but on it's side... You find them also on Sinclair QL and some models of Sinclair Spectrum ( eg, the original 128K model ).
Getting crimpers for them is hard. I have a metal former I can use with pliers, but one day I'll get the proper crimper.
BS 6312 is the number for the specification for the plug.
David