The UK Army receiving valve AR was made with the I/S4 and I/S3 interservice base. The AR3 seen here is fitted with an I/S2 base. The AR series had the 2.0 Volt 0.4 Amp filament rating. These are dull emitter valves with a thoriated tungsten wire as the emitting surface.
The base is 30 mm vertically not including the pins. The handle indicates that it was pushed into the socket horizontally.
This exhibit was used in the A&C receiving set.
The anode connection.
The underside of the base. The pins are the filament connections and the side plates are connections for anode and control grid.
The grid connection side plate. There appears to be clear adhesive tape on the glass.
The electrode assembly. The lower support connects to the top end of the filament (now broken). The middle support connects to the top of the grid.
A closer view of the top of the anode. The flat tape of the filament tension spring can be seen together with the fold to hold the thoriated tungsten wire. The top of the grid helix is also visible.
The thin glass tube envelope is 23 mm in diameter, and excluding the I/S2 base pins is 84 mm tall.