Erlang (unit)
The erlang (symbol E) is a dimensionless unit that is used in telephony as a measure of offered load or carried load on service-providing elements such as telephone circuits or telephone switching equipment. For example, a single cord circuit has the capacity to be used for 60 minutes in one hour. If one hundred six-minute calls are received then the total traffic in that hour is six hundred minutes or 10 Erlangs.
In 1946 the CCITT named the international unit of telephone traffic Erlangs in honor of Agner Krarup Erlang.
Read more about Erlang (unit): Traffic Measurements of A Telephone Circuit, Erlang B Formula, Erlang C Formula, Engset Formula