1889: Almon Strowger invents the automatic switch
1891: Strowger forms Automatic Electric Company, and receives switch patent
Bell System adopts rotary dial switching
1938: Crossbar switching introduced
1951: The Step-By-Step Switch
1958: Conversation Crossroads, a Surreal Look at Telephone Switching
1965: No. 1 ESS switch enters commercial service
1965: Electronic Switching System, Central Office Debut (Bell System)
1971: Hoover invents computerized call switching
No. 4 ESS digital toll switch deployed
Northern Telecom DMS-100 digital switch
Siemens debuts digital telephone switching
1984: Speedy Cutover Service, SXS to ESS (AT&T)