Telephone crossbar switch, Swedish Ericsson, 1921
1921
1921
1918
1920
1919
1920
circa 1920
1934
1918
circa 1920
1955; 1830
1921
1918
2000-100 BCE
1918-1920
1918
circa 1920
1920
1920
1919
1990-96
1920
1921
1920
1934
circa 1919
1772 (original); 1919 (model)
1918-1920
1930 (replica); 1834 (original)
1918
1903 (original); 1982 (model)
circa 1920
4000-2001 BCE
1830 (original); 1967 (model)
1801-1892 (prepared); 1946 (element replaced)
1919
1919
14 May 1921
circa 1921
circa 1918
1920
1730; 1967
1918
circa 1918
1972-3
2500 BCE
1920
1950-1920
circa 1918
1919
1919