Radio News Sylvania Ad, February, 1947
This colorful back-cover Sylvania advertisement trumpets the virtues
of "lock-in" (also known as "loktal") tube sockets. This type of
socket was suitable for wartime applications, where lots of jolting
and vibration was to be expected. Sylvania's lock-in ads ran throughout
that year. Another ad from September, 1947 is
typical of the series.
The loktal design was popular for a few years following
World War II, but was quickly superseded by
all-glass "miniature" tubes, which were smaller,
lighter, and cheaper to make.
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