Sorry I missed the bit about who you
wanted shooting down
Specifications are very useful because
they give you all the information you need to design something.
If the end result is wrong but it meets the specification then
the spec was probably wrong or something important was forgotten
about when the spec was written.
A couple of very clever engineers were
given the job of designing a radio interfacing system.
The system interconnected lots of different
radios and radar operators via a computer, which did the organising,
and a collection of switches which did the routing for microphones
and headsets.
Say for example a radar operator wanted
to launch a missile at an aircraft in his sector, he would call
the SAM chap and give him the instructions. To do this his microphone
would need connecting to a particular transceiver tuned to the
frequency of the SAM operators radio.
Or if the radar chap wanted to guide
an interceptor towards an enemy aircraft he needed to talk to
the pilot and therefore be connected to an Air-Ground-Air type
of radio transceiver.
The system being designed allowed all
this to happen.
Instructions for doing the various tasks
were carried out by merely touching a screen scanned by infra-red
detectors which would recognise the screen position (where there
was a legend such as "Connect to AGA") and allocate
and set up a free radio of the type required.
The young chaps, whom this story is
about, had recently joined us from another site and were very
keen to show us how professional they were.
We hadn't bothered much with specifications
until then and if we did they were usually written after we'd
done the designing.
This always ensured the spec matched
the end result.
Anyway the two spent ages writing extremely
clever specifications full of dB's and complicated technical
expressions.
And of course no-one in the Industry
had the right bits required to meet the specifications and therefore
lots of tenders had to be issued for the design of audio filters,
special matching transformers and voice operated gain adjusting
amplifiers and the like.
At last suppliers for all the relevant
bits were identified and the bits ordered and bread-boarding
commenced.
Costs were very high but the end result
was a set of equipments that would perfectly match their specifications.
The proof was there because all sorts
of exotic and expensive test gear had been acquired, and where
it wasn't available, specifications for new stuff was produced,
and other engineers hired to design and build it. All the components
met their specs. Some had been rejected and sent back for rework
but eventually everything was just right.
radar consoles
a "voice"switch
Artificial ears, special voice recordings and suchlike were gathered
together and finally a complete trial system was constructed.
Everything worked and everything met
the specifications to the nth degree.
Orders were placed for thousands of
components and detailed manufacturing drawings proceeded apace.
Later, Jim, an engineer who was just
passing the door of the special laboratory, wherein the works
had taken place, and the first "public" demonstration
was to be made, was summoned at random.
"Put on the headphones Jim and
listen to this".
It was the first live test with a real
microphone and a real headset.
First a direct connection from the microphone
to the headset…..then a connection via the new system.
"What do you think?" asked
the pair of proud engineers.
"The first test was really good
but the second was a bit muffled", said Jim.
A second opinion was sought; someone
with good hearing was needed.
"What do you think", they
asked.
"It's really good said second opinion,
really clear".
"That's without our system",
was the annoyed response, "Listen to THIS!".
"It's very muffled", said
second opinion.
What they'd forgotten was that over
the years, air traffic control headsets and microphones developed
in pace with each other.
Neither was very good individually but
together, results were quite acceptable.
To give good fidelity into a typical
ATC headset the audio into it was nothing like flat but our new
system processed the audio into a perfectly flat chunk having
a variation of less than 0.5dB across a band of 300Hz to 3000Hz
with a cut off at the sides like Beachy Head.
Unfortunately the headset needed lots
of top, which the ATC microphone had, but which our system had
removed!
By then we'd ordered thousands of special
filters and transformers, the Drawing Office had drawn up all
the circuit boards and manufacturing was already under way.
Too late!
Maybe the Radar Operators developed
a special squeaky voice to make themselves understood, I don't
know.
