activities based on the interception of military radio and telephone
traffic proceeded apace. It would be many years though before
the words "SIGINT" and "COMINT" would be
coined, and intelligence to be assimilated and disseminated fast
enough for it to make much difference. The first substantal organisation
had Bletchley Park as HQ, then later it was GCHQ in Cheltenham
(where I once used to work). Six key aspects are involved: identification
of what to tune in to; interception and storage of information;
decryption so it can be read; translation into English; analysis
of usefulness and working out who might benefit; then dissemination
to customers (which of course, nowadays, usually means re-encryption).
Alongside developments in communications,
and advances in the speed of providing information to those who
most needed it, were developments in coding and cryptography,
aimed at slowing down or completely preventing the gaining of
intelligence from intercepts.
This is an amplifier made by
the same firm that designed the cryptographic equipment whose
key was cracked by the Enigma computer at Bletchley Park some
twenty odd years and a war later.
When a telephone was used to
signal from a WWI trench an earth connection was usually made,
and through the earth connection a signal flowed into the ground.
The majority of the signal took the easiest path between sender
and receiver but lots of current also passed by more roundabout
routes. Because trenches rarely followed straight lines anyway,
a good proportion of the earth current was detectable at nearby
German trenches and if connections were made to ground at two
widely separate points enough of the current was available to
drive a sensitive detector. The amplifier shown used four triode
valves and was able to amplify tiny intercepted earth currents
sufficiently for an eavesdropper to listen in on enemy communications.