The earliest mention I can find of 572Bs existing is in the 1962 ARRL Handbook,
and for some time, the only manufacturer appeared to be Cetron. In that
Handbook, the listings for it are as Class B push pull modulator, which makes
sense, as it isn't really built as an RF tube. It seems that some Cetron tubes
were rebranded by other tube manufacturers (not an uncommon arrangement), but
it's relatively recently that the Taylor name has been resurrected in China. I
wonder if anyone will ever try resurrecting Heinz and Kaufman's 'Gammatron'
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