The EM80 miniature tuning indicator produces a fan shaped display in green. Mullard describe the EM80 as a tuning indicator for use in FM or AM receivers. The grid voltage range is 13 Volts. Electrically it is similar to other tuning indicators, the valve consists of a triode amplifier that is linked to the indicator device. The control of the image is effected by the triode cathode being connected to the display grid.
The curved target is coated with phosphor on the inner surface. The smaller curved plate shields the voltage amplifier from view.
Face view of target and lower cosmetic shield.
The amplifier triode lays horizontally across the valve.
The heater is coiled and insulated to form a wire that is formed as a hairpin to pass as two strands through the cathode.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 58 mm tall.
References: Data-sheet & 1040. Type EM80 was first introduced in 1954.