On Wed, 15 Oct 2014 18:30:46 -0000, wrote:

The straw that broke the camel's back was a thing that had built in self
test, which was OK, but there was also self test for the self test, and
self test for the self test for the self test...

Chuckle. I had much the same problem except that the self test
function was aptly named BITE (Built In Test Equipment). All too
often, the radio would be fully functional, but the system would be
down because the BITE was complaining about something spurious.
Someone suggested a second BITE to monitor the first. That was
prototyped by some other engineer, which further reduced the
reliability of the system. Eventually, I was handed the mess, with
instructions not to spend any money, not to change anything, and get
it done before my boss returned from vacation (so he couldn't be
blamed if anything went wrong). My solution was to redesign the
interface between the radio and the BITE so that the BITE boards could
be removed without affecting the operation of the radio. The result
was predictable. All the BITE boards were immediately removed on
arrival by the customer, thrown into an unmarked cardboard box, and
left to rot while the radios continued to operate normally without
them.

Morals: Complexity does not improve reliability and the first thing
to fail is usually the fail safe.




--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558