The EIA (Electronics Industries Association - or Alliance) Recommended Standard No. 232. Yes, boring I know, but there it is. smile

With the ubiquitous D-type serial connector, you can also get at each connection (you can't do that with a USB data stream). And, as I've already alluded to, some of those pins may be nothing to do with data at all, but simply battery voltage levels etc. Always check the service manual for details!

If you don't inspect ... don't expect.