The CV493 is the commercial 6X4 HT rectifier. A common cathode is employed passing through two anodes arranged at right angles to one another.
At 325-0-325 input to the rectifier this will give an HT rail higher than is required for most domestic equipment. Use for audio amplifiers and small transmitters is most probable, or driven at 250 volts for radio receivers.
The KB/FB identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the FB identifies the maker as STC, Footscray.
The central cathode with two identical anodes that with one inverted and rotated by a right angle fit the maximum radiating area into the small envelope.
The visual effect is of an X shaped anode.
See alsoEZ90 from Brimar and the 12X4 12 Volt heater version.
The thin glass tube envelope is 18 mm in diameter and the length, excluding the B7G base pins, is 59 mm.
