The CV248 photocell is designed to operate with 160 Volts on the anode and was based on the commercial GS16.
Construction is a photosensitive semi-circular cathode with a rod anode at its centre all mounted on a conventional pinch.
The KB/RCY identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the RC identifies the maker as Ferranti, Chadderton, Oldham.
The curved photo-cathode on the right with the loop anode in front.
Face view showing the anode loop around the edges of the cathode.
Taken from the top - semi-circular cathode and glass bead for the anode supports.
The thin glass tube envelope is 25 mm in diameter, and excluding the B4 base pins is 58 mm tall.
