Hot stuff this computer gear!
A long time ago now it was decided to
expand a certain large Defence Contractors' Software Design Department's
sphere of interest.
In the early days of integrated circuits
and the Cold War there were loads of opportunities for selling
bits of kit to NATO.
Combining the marketing function into
the said Software Department's responsibility paved the way for
near disaster. The Department was able to operate totally independently
to the rest of the Company wherein resided experience in matters
of particular skills.
When the first of 22 special communications data processing equipments,
"vital to the defence of the free world", was sent
down an ex-coal mine in Belgium to a NATO Comcen the first of
many problems surfaced.
The "programmers" came back from NATO HQ to a heated
meeting with senior managers. "We thought that when the
specification called for "TEMPEST" it meant something
to do with the weather," was the comment by the Project
Manager, "But," he said, "We cracked on we knew
all along what they meant and said this was just a prototype".
Unfortunately, to the software people,
"TEMPEST" had just been a word, and unless you knew
about it in those days, it was. Other Departments knew, but of
course, because of the new way of operating, THEY hadn't found
out about the "Message Heading Generator" until too
late.
"TEMPEST" is the expression
used by the "cloak and dagger" agencies to cover the
specification of an equipment's electro-magnetic radiation and
signal leakage. In order to meet TEMPEST requirements the equipment
must not emit any radiation or conduct anything to its output
which may impart to a listening third party any useful intelligence.
For example if one was to park one's car in a busy commercial
street and operate a suitable television receiver conected to
a high gain directional aerial one could view information being
displayed on a nearby computer screen. Commercial equipment will
radiate all sorts of noise, some of which can be resolved, by
an expert, into information. Military equipment used for sensitive
applications must not be allowed to radiate information to all
and sundry. The maximum levels of radiation and conduction permitted
for these equipments is covered by TEMPEST.
Inexperienced electrical and mechanical
designers had been roped in to help out the programmers in what
was seen as a piece of software in a tin box.
After spending loads of money it eventually got sorted out and
22 equipments were delivered all over Europe. Soon however we
got reports of failures. The MHG design engineer helped out and
new components were fitted. These failed in turn and such was
the standing of the Defence Contractor that the failures were
automatically attributed to the component supplier.
Still failures occurred. Eventually,
when all 22 failed equipments had been returned to the factory,
Allan was asked to look into the problem and find a new supplier
for the rogue component with an "abysmal MTBF".
Each of the eight communications interfaces was made of discrete
components including an enormous stud-mounted 80 volt zener diode.
When an interface wasn't being used its zener diode dissipated
loads of power and went close to melt-down. In the chill of our
laboratory they survived…just. When in a nice warm Comcen
they didn't.
Looking at the manufacturer's curves,
rather than the optimistic max power in watts on an infinite
heatsink at the North Pole, the poor zeners, with no heatsinks,
were operating miles outside their spec., and at times their
junction temperatures must have been close to the temperature
of the sun!
Because of the threat of having to re-test, I had to work out
a solution which used the original circuit board, the same circuit
track, as many original components as possible AND wasn't obvious
to the customer AND allowed shortcomings to rest with the zener
supplier. I did, it worked, and our reputation emerged spotless.
