THORPE K4, 1927

Helix wound anode valve. The Thorpe K4 was a tetrode of the space charge grid type. It was intended primarily for use in the Unidyne or Solodyne circuits which were popular at that time.
The advantage of this valve was that no separate anode voltage supply was required, as both anode and inner grid were fed from the 6 volt filament battery. In the period 1925-1927 the K4 valve was offered for sale by at least three vendors in London, but although distributed by Bower Electric Ltd was not advertised by them.

A0598