1950 - The first step-by-step PBX system was introduced.

1952 - Telephone service via aluminum cable was being tested.

1954 - After satisfactory trials, recording trunks for PBXs are offered.

1957 - Bell Labs starts development of the magnetic tape machine which is capable of transmitting at speeds 16 times faster than teletypewriter machines.

          -Bell Labs starts the development of a high speed digital computer named Leprechaun under an Air Force contract.

1954 - After satisfoctory trials, recording trunks for PBXs were offered.

1957 - Bell Labs starts developement of a high speed digital computer called Leprechaun under Air Force contract.

1958 - Bell Systems announces its Data-Phone service, which permits high-speed data to be sent over POTS lines.