
One of Fleming's first thermionic diode valves, 1889
1889
1889
1897-1898
1839 (original); circa 1988 (replica)
1897
1801-1840 (original); 1901 (model)
1890-1891
1889
1898
1895
1890
1892
1897
circa 1890
circa 1890
circa 1890
circa 1890
1889
1872 (original); 1909 (model)
circa 1897
1898
1890
1896
1896
About 1890
1890
1889
1896
1934
1896
1892
1897
1895
1896
1898
before 1889
before 1889
1894
1893-4
1890-1896
1890-1894
1890-1894
1890-1894
1898
2000-100 BCE
1955; 1830
1898
1893
1897
1896
1895