StarLAN (original) (raw)

StarLAN was the first implementation of Ethernet computer networking on twisted pair wiring.

Developed in the mid 1980s by members of the IEEE 802.3 standards committee, StarLAN ran at a speed of 1Mbps. This version of the standard was known as 1BASE5. It was adopted by other networking vendors such as Hewlett-Packard and Ungermann-Bass.

StarLAN provided the basis for the later standard 10BASE-T. With the addition of link beat, a feature to easily detect whether or not a cable was connected, and later full-duplex, a feature that enabled systems to transmit and receive at the same time, StarLAN's basic modulation scheme became 10BASE-T.

A major design goal in the StarLAN technologies was compatibility with analog telephone signals in the same cable bundle. The signal modulation and wire pairing used by StarLAN were carefully chosen so that they would not affect or be affected by either the analog signal of a normal call or the 20Hz high-voltage analog ring signal.

The TIA-568B wiring pinout standard was chosen, and pair 1 (blue) was left unused to accommodate an analog phone pair. Pairs 2 and 3 (orange and green) carry the StarLAN signals. This greatly simplified the installation of combined voice and data wiring, which was revolutionary in 1990.