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The '''Octal tube base''' was introduced in 1935 by RCA for their new metal envelope tubes. | The '''Octal tube base''' was introduced in 1935 by RCA for their new metal envelope tubes. | ||
The glass envelope of an octal base tube is cemented into a bakelite or plastic base surrounded by eight metal pins on | The glass envelope of an octal base tube is cemented into a bakelite or plastic base surrounded by eight metal pins on a 17.45 mm (11⁄16 in) diameter circle in 45° increments. | ||
The wire leads from the tube were soldered into the pins, | |||
and the seal-off tip through which the air was evacuated from the envelope was protected inside a 7.82 mm (5⁄16 in) diameter keyed post in the center | |||
whose key fits an indexing slot in the socket so the tube can only be inserted in one orientation. | |||
Matching plugs were also manufactured that let tube sockets be used as [[Octal connector|eight-pin electrical connectors]]. | Matching plugs were also manufactured that let tube sockets be used as [[Octal connector|eight-pin electrical connectors]]. |