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The 9-pin B9A (Noval) tube base was developed in the late 1930s for miniaturized all-glass tubes, with the earliest tubes using this base commercially introduced in the early 1940s.
The pins are arranged evenly in a circle of ten evenly spaced positions, with one pin omitted, which allows the tube to be inserted in only one orientation. The pins are stiff wires protruding through the bottom of the glass envelope and plug directly into the socket. The base is an integral part of the glass envelope. The pinched-off air evacuation nub is at the top of the tube.
B9A is the most common base for tubes from the 1940s to the 1960s.
- Miniature tubes @ Wikipedia