
De Forest audion 1906-1915
1906-1915
1906-1915
1839 (original); circa 1988 (replica)
1907
1910
1915
1912
1906
1910
1910
1914
1910
1908
1909
1912
1915
1906
1907
1913
1872 (original); 1909 (model)
1915
1915
1911
c.1912
1910
1916
1955; 1830
1934
circa 1910
1914
1914
1915
1906-1916
1906
1915
2000-100 BCE
1914
1914
1914
1914-1916
1910
1907
1913
1907
1801-1892 (prepared); 1946 (element replaced)
c.1912
c.1912
1911
1930 (replica); 1834 (original)
1915
1913