1919
1921

1920

C.1920 Gray Telephone Pay Station Co Hartford CT
C.1920 Gray Telephone Pay Station Co Hartford CT
Gray Telephone Pay Station
Demonstration telephone
Demonstration telephone
E. F. Caldwell & Co. Custom Handmade Candlestick
E. F. Caldwell & Co. Custom Handmade Candlestick
Gray Three-Slot Payhone
Gray Three-Slot Payhone
Gray Telephone Pay Station
Keystone Dial Candlestick
Keystone Dial Candlestick
American Electric Keystone Telephone
Siemens & Halske Naval Telephone
Siemens & Halske Naval Telephone
Siemens and Halske 25-extension intercom
Siemens and Halske 25-extension intercom
Siemens
Tønsberg Telefonforening telephone
Tønsberg Telefonforening telephone
Otto Zobel invents m-derived filters
Otto Julius Zobel
PDF: AT&T Annual Report, 1920
AT&T Annual Report, 1920
After acquiring Puerto Rican and Cuban telephone companies, the Behn brothers found ITT
Sosthenes Behn
PDF: Select-O-Phone intercom system brochure
Select-O-Phone intercom system brochure
Dial phones spread to major cities