The X109 is a triode hexode mixer for operation at up to 100 MHz and designed for circuits with series heater chains as found in receivers for use on both AC and DC mains. In the UK a DC mains supply still existed in some places at the end of the 1950s and a few isolated areas had DC mains into the 1960s.
The Marconi paper label on this M-OV made valve. Marconiphone was a consumer brand.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 48 mm tall.
References: Datasheet & 1040. Type X109 was first introduced in 1951.
Absolute Maximum Operating Conditions¶
Updated January 09, 2017.