1920 To 1969
- 7 March 1926: First transatlantic telephone call, from London to New York.
- 7 January 1927: Transatlantic telephone service inaugurated.
- 7 April 1927: world's first videophone call via an electro-mechanical AT&T unit, from Washington, D.C. to New York City, by then-Commerce Secretary Herbert Hoover.
- 28 May 1927: Rotary dial service was started from midnight.
- 1935: first telephone call around the world.
- 1941: Multi-frequency dialing introduced for operators in Baltimore, Maryland
- 1946: National Numbering Plan (area codes)
- 1946: first commercial mobile phone call
- 1946: Bell Labs develops the germanium point-contact transistor
- 1947: December, W. Rae Young and Douglas H. Ring, Bell Labs engineers, proposed hexagonal cells for mobile phones.
- 1948: Phil Porter, a Bell Labs engineer, proposed that cell towers be at the corners of the hexagons rather than the centers and have directional antennas pointing in 3 directions.
- 1951: Direct Distance Dialing (DDD) first offered at Englewood, New Jersey, to 11 selected major cities across the United States; this service grew rapidly across major cities during the 1950s
- 1955: the laying of trans-Atlantic cable TAT-1 began - 36 circuits, later increased to 48 by reducing the bandwidth from 4 kHz to 3 kHz
- 1958: Modems used for direct connection via voice phone lines
- 1960: ESS-1
- 1960's: Bell Labs developed the electronics for cellular phones
- 1961: Touch-tone released to public on trial basis
- 1962: T-1 service in Skokie, Illinois
- 1963: the first publicly available push-button telephone was released, by Bell Systems/Western Electric, in the towns of Carnegie and Greensburg, Pennsylvania.
- 1965: first geosynchronous communications satellite - 240 circuits or one TV signal
Read more about this topic: Timeline Of The Telephone