The VT75B beam tetrode is specified for both audio use and television line output service. The VT prefix indicates that this was made to a UK Air Force specification and was renamed the CV1577 with the advent of the CV register.
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 lettering gives the VT75B, the old stores code of 10E/472 and the code ZOKJ all etched into the glass.
The envelope also carries the standard M-OV etched ellipse with the commercial Type designation of KT44. The end wall of the anode is solid whereas in the almost identical KT45 the end wall is mainly open.
The classic envelope is 56 mm in diameter and, excluding the B7 base pins, is 137 mm tall.
References: Data-sheet & 1043. Type VT75B was first introduced in 1939. See also1939 adverts.
