Telephone crossbar switch, Swedish Ericsson, 1921
1921
1921
1920
1919
1920-1925
1920
1924
1925
1922
1923
1924
1925
1922-1923
1922-1923
1922-1923
1922-1923
1923
circa 1920
1934
2000-100 BCE
1924
circa 1920
1955; 1830
1921
1923
1925
1920-1925
circa 1920
1920
1920
1919
1925
1990-96
1922-1925
1920
1924
1922-1924
1923
1922-1923
1922-1923
1922-1923
1922-1923
1922-1923
1920-1922
1921
1925
1920
1934
1922-1923
1922-1923
1923