In article ,
wrote:
A parameter who's function is not listed in the book so I
didn't know what it did. But I had written down all the parameters
when I bought the machine

Very wise!

All I did was change a 0 back to a 1. I wonder how the damn
parameter changed in the first place?

Might have been a bit flip in memory somewhere (cosmic ray, bad IC,
etc.).

Or, is possible to change those parameters under software control that
doesn't require the manual "parameter unlock" switch? A garbled
command sent to the device - even a one-character error in
transmission - might have "silently" changed a parameter in an
unexpected way.

Or, maybe, this parameter was changed as a side-effect of some other
(legal and reasonable) command?