The CV242 photocell is designed to have an anode voltage of 80 Volts and has a sticker to indicate this.
The KB/D identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the D identifies the maker as Mullard Radio Valve Co., Mitcham.
The cathode is a flat plate that is folded to form a half cylinder.
The anode is a single vertical rod supported only at the base.
The thin glass tube envelope is 25 mm in diameter, and excluding the B4 base pins is 78 mm tall.
