Driver's brake valve with feed valve. Secti

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

V24 and Q amplifying valves, c 1920s.

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

5-valve R1 Radio receiver, 1922.

Ros 'pop' safety valve, c 1904. This is a

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

Mitral and aortic replacement heart valves, 1970s.

Woman with Marconi transmitting valve, Radiolympia, London, 1936.

Two Starr-Edwards artificial cardiac valves, 1978-1979.

Two Starr-Edwards artificial cardiac valves, 1978-1979.

'How to build a two valve set', No 23, Godfrey Philips cigarette card, 1925.