[NTLK] NewtonTalk Digest, Vol 144, Issue 16

[Matthias Melcher]

> On 31. Dec 2025, at 12:12, Helmut Fischer via NewtonTalk <newtontalk at newtontalk.net> wrote:
> 
> I am not sure whether you are aware of the difference between the formerly very common RS232 connections, most probably also used by your camera, and the RS424 standard Apple used for Macs and Newtons (should be covered in the FAQ, but I didn’t check).

Yes, you are right. Apple uses the LTC1232 (https://www.analog.com/media/en/technical-documentation/data-sheets/lt1323.pdf) for their LocalTalk protocol. Some of those signals (RxD and TxD) use RS422 levels and generally need a level converter to connect to RS232 or TTL logic.

Apple was very aware that modem use RS232, so they designed those chips to tolerate RS232 signals. They do not generate RS232 though, and not every receiver can interpret what comes out of the LTC (as a result many RS232 USB converters don't work).

There are cables advertised that are supposed to connect RS232 to the Apple Mini DIN, but I have no idea if the work for the Newton: https://www.amazon.de/JSADZKJ-Serielles-M%C3%A4nnlich-Schraubklemme-Adapterkabel/dp/B0DPHST5GT?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=A1Y8QMS5L48IXF

These are the internals of those cables:

https://www.dr-lex.be/random/pcmodemmaccable.html