In 1946 the erlang became the standard unit for communications traffic for the International Telegraph Union. Now the standards are administered by the ITU Telecommunication Standardization Sector (ITU-T). For a while it was called Comité Consultatif International Téléphonique et Télégraphique when the UN became involved.

The erlang is named for the Danish mathematician, statistician and engineer Agner Krarup Erlang (1878 - 1929) who is in the picture. He came up with the initial formulae. It was published in 1909 in his first work The Theory of Probabilities and Telephone Conversations. This was during the era where human operated cord boards prevailed but the concepts hold true even in the information age.

An erlang is a dimensionless unit defined as one circuit in use continuously over a measured period of time. The time is often, but not always, one hour. Shorter periods may be used for traffic spikes such as may occur during commercial breaks in popular TV programs. World communications traffic has a one day spike on each country's mother's day.

Traffic of two erlangs could be two circuits in use continuously, four circuits in use half the time, eight circuits in use one quarter of the time and so on.

The formulae can be used to predict the possibility of overload or call blocking as well as forecasting capacity requirements.

Erlang is now also the name of a programming language probably in honour of the same genius.

More Info: www.erlang.com