Telephone crossbar switch, Swedish Ericsson, 1921
1921
1921
1920
1920
circa 1920
1934
2000-100 BCE
circa 1920
1955; 1830
1921
circa 1920
1920
1920
1990-96
1920
1921
1920
1934
1903 (original); 1982 (model)
circa 1920
4000-2001 BCE
1930 (replica); 1834 (original)
1801-1892 (prepared); 1946 (element replaced)
1830 (original); 1967 (model)
1989-08
14 May 1921
circa 1921
1920
1730; 1967
1972-3
2500 BCE
1920
1950-1920
circa 1920
1920
1920
1970-1910
circa 1920
1920
1971-1900
1990-95
1921
1920
1920
1921
1921
1920
1920
1965-1900
1859; 1986
1920