The UM11 is a tuning indicator designed for operation with a series heater chain. The EM11 has the same pin connections and was designed for parallel heater connection across a 6.3 Volt supply. For universal (AC/DC) sets without a mains transformer the maximum HT available was limited to the mains voltage and so the UM11 was designed to operate at lower voltages than the EM11.
The UM35 has the same electrical characteristics but is fitted with an IO base.
The amplifier triode is located below the target.
The electrodes in close-up. The wire grid is visible as is the wire helix in the target.
The two triode anodes with the display on the right.
The grid winding is clearer in this image as are the lower connections and supports sealed within the pinch.
The target construction.
The wide glass tube envelope is 36 mm in diameter, and excluding the footless base pins is 76 mm tall.
References: Data-sheet. Type UM11 was first introduced in 1940. See also1940 adverts.
