The CV4047 (commercially the G400/2G) is a voltage stabiliser that dates to 1957.
The KB/F identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the F identifies the maker as STC, Paignton.
The envelope also has the STC logo and the commercial Type designation of G400/2G.
The anode connection wire 4 is internally shielded with a ceramic tube to prevent the discharge from occurring outside the defined region. The double mica indicates that the valve is rated for operation in areas of shock and/or vibration as in aircraft.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G/F wires, is 42 mm tall.
References: Data-sheet. Type CV4047 was first introduced in 1957. See also1957 adverts.
