The L610 is an early example of an audio output valve designed to drive a loudspeaker in a domestic radio receiver. It dates from 1929 and was for battery operation.
The L610 was the lineal descendant of a series of similar valves including the DEL612 (thoriated tungsten filament) and the DEH610 (barium-coated filaments using the Azide process).
This exhibit has a blackened bulb typical of the Azide process. Our other L610 has a clearer bulb and was made using an oxide coated filament.
The Osram brand label - a consumer product.
The dome carries the identification. The lettering is feint but can be read under the right lighting.
The balloon envelope is 46 mm in diameter and, excluding the B4 base pins, is 83 mm tall.
References: Data-sheet & 1043. Type L610 was first introduced in 1929. See also1929 adverts.
