I've posted this before so sorry for the repeat at
https://www.electrical-contractor.net/ubb/Forum9/HTML/000063.html . Here is the old (pre-1990) South African standard. There are six contact surfaces: The outer pair are line 1 and the inner pair line 2. I assume the intermediate pair (not connected in the photos) would be line 3.
RSA now used the US standard as found on the back of your PC.
As PaulUK mentioned in the thread referred to above, it is similar to the older Australian phone jacks (these appear to have an extra pin with an additional pair of contacts that makes the design asymmetric). I was lucky enough to get a look at one of those in situ recently.
[This message has been edited by Hutch (edited 11-03-2002).]