BigWallop wrote:

Now that's a good point Bob. But I'm now wondering how many pages of
drawings I'll have to make up if the system goes to the full ten switches.
:-))

9,999 detectors on one system is highly unlikely though, so I might give him
a try on this.

What is the likely highest number?

I agree that he clearly has a mental block, and the anxiety induced by
constantly getting it wrong (and knowning that you know) will be making
it worse.

You definately need to make a fresh start, beginning with what he can
do and feels confident with, and building on that.

I'd prepare sheets with drawings of actual switch settings and the
associated numbers. On A4 sheets in landscape you ought to be able to
to get 8 diagrams across the page in a line. So the first line will
have 0-7, the second 8-15 etc.

You might get 16 lines to a sheet so that would allow 0-255 on a
double side which could be laminated. With luck, he may work out
the pattern for himself, but don't push it. Otherwise limit his
responsibilities to jobs which are within his capabilities using
the crib sheet.

Nick