I don't know this code specifically. The thread below calls it a RB ( roll Bar ) limit SW.

3) 114 Limit switches (S84/4) Soft top close
4) 124 RB faulty limit switch signal illogical
5) 122 limit switch (a83/1) roll bar stowed

http://www.peachparts.com/shopforum/tech-help/322246-1997-sl500-convertible-top-operation.html

It also shows codes that this particular person has. By using their list and a full code list, by a process of elimination you should be able find all SW and verify 124 is for the roll bar.