About the only tubes that used the 11 pin base were photomultipliers like the 931A type used in the B&K TV analysts. They were pretty common on industrial relays, allowing 3 SPDT contact sets, and 2 pins for the coil.
The 11 Pin plug/socket were also pretty commonly used for connecting external power supply units to vintage ham transceivers. Like the HP-23 supplies used with the Heathkit SB-line.
Last edited by N2IXK; 05-02-2018 at 10:45 AM.
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