Woman examining Mullard valves, Radiolympia, Olympia, London, 1934.

Valve-operated radio, 1955.

Radio valve of Clearton valve type.

Marconiphone crystal-valve radio receiver, 1923.

5-valve R1 Radio receiver, 1922.

Radio pick-up arm, 1932 and klystron valve, 1940.

Diode valve, early 20th century.

Early commercial two-valve radio receiver, 1920-1921.

Ekco 'Mains Drive', three-valve radio receiver, 1929.

Brisez's bi-valve intra-uterine speculum, French, 1841-1900.

Loewe multiple valve radio receiver, late 1920s.

Driver's brake valve with feed valve. Secti