The CV1577 beam tetrode is specified for both audio use and television line output service. Originally the RAF used this valve as the VT75B and it was renamed the CV1577 with the advent of the CV register in 1941.
In the television role the valve can withstand a positive anode surge of 8,000 volts and it was television service it was mainly specified. The anode connection is taken to a top cap so that the valve can withstand high peak anode voltages.
The specification is very close to the M-OV KT44 and indicates a part of their Kinkless Tetrode (beam tetrode) series.
The anode is partly open at the grid ends and the inner structure is visible. The working faces of the anode have side flanges for greater heat dissipation.
The bright plates are the beam forming plates and the inner wire grids are shaped to pass flat across the cathode tube. The control grid is wound on copper supports and is topped by heat radiating fins.
The classic envelope is 56 mm in diameter and, excluding the B7 base pins, is 130 mm tall.