The examples shown in the following
pages were all developed up to and during WWII. Some were for
applications kept very secret until their appearance years later
in "government surplus" equipments which were sold
to experimenters and radio hams from shops which sprang up in
most large cities in the UK.
Other types were developed for
use in transmitting equipment or for instrumentation.
I haven't included the common
types used in radio, Hi-Fi or television receivers as most people
will have seen examples of these.