The DC3/HL has a 25 Volt 100 mA filament and the DC/HL runs from 6.0 Volts at 500 mA both are indirectly heated. The characteristics of the DC/HL differ slightly from the DC3/HL.
Both versions are described as detector or audio triodes. The DC3/HL would be suitable for use in a series heater chain.
The triode section housed between mica sheets.
The Type designation is on the dome of the envelope.
Thanks to Mark Mallison for sending the images.
The classic envelope is mm in diameter, and excluding the B5 base pins is mm tall.
References: Data-sheet & 1043. Type DC3/HL was first introduced in 1931. See also1931 adverts.
