
One of Fleming's first thermionic diode valves, 1889
1889
1889
1897-1898
1902
1839 (original); circa 1988 (replica)
1897
1801-1840 (original); 1901 (model)
1890-1900
1890-1891
1889
1898
1899
1901
1895
1901
circa 1900
1899
1890
1892
1897
circa 1900
1901
1900
circa 1890
circa 1890
circa 1890
circa 1890
1892-1902
1889
1872 (original); 1909 (model)
1898
circa 1900
1900
circa 1897
1898-1899
1901
1898
1890
1901
1902
1896
1896
About 1890
1890
1889
1896
1901
1899
1899
1934
1901