The DER triode from Marconi dates from 1922. The filament is thoriated tungsten and so emission is achieved at a lower temperature than with pure tungsten, hence the description dull emitter. The construction is of a cylindrical anode with a helical grid passing through it, that in turn is threaded by the filament.

The balloon envelope is 43 mm in diameter and, excluding the B4 pins, is 80 mm tall.

More

This exhibit was last updated on 02 December 2007