Round_Type-N

The Type N is a "soft" triode, actually the second early triode in the UK after the Round type C. Type N has an asbestos pellet in a 10 mm tube above the envelope. Quite different to the von Lieben Triode is also the grid, but similar to early Papaleksi tubes. Both, Lieben and Papaleksi use an apendix, but not for Asbestus, but Quicksilver Amalgam. The Round Type N triode was first used in the Marconi Receiver Type 27 from 1914 (or 1915) to 1918.