Louden valves were marketed by Fellows Magneto Co. Ltd. from 1924 to 1927. Some Louden designations used were F1 and F2 for bright emitters; FER1, FER2 are the corresponding dull emitter tubes having thoriated filaments.
Bibliografia
Saga of the Vacuum Tube, Tyne page 392
Wireless World (The), London (WW, 79) June 24th 1925 p652
British Radio Valves - The Classic Years: 1926-1946
FER1_4Volt: Fin Stewart
Fin Stewart
Just Qvigstad
FER1_4Volt: Banneitz, TB der drahtl. Teleph. 1927
Anonimo 15 Collezionista
