[4] By the time of his relatively early death at the age of 51, Erlang had created the field of telephone networks analysis.

His early work in scrutinizing the use of local, exchange and trunk telephone line usage in a small community to understand the theoretical requirements of an efficient network led to the creation of the Erlang formula, which became a foundational element of modern telecommunications network studies.

[2]: 10-12 A distant relative provided free board and lodging, and Erlang prepared for and took the University of Copenhagen entrance examination in 1896, and passed with distinction.

[2]: 14 He was a member of the Danish Mathematicians' Association (DMF) and through this met amateur mathematician Johan Jensen, the Chief Engineer of the Copenhagen Telephone Company (KTAS in Danish), an offshoot of the International Bell Telephone Company.

[2]: 18 While working for the CTC, Erlang was presented with the classic problem of determining how many circuits were needed to provide an acceptable telephone service.

[2]: 17 The British Post Office accepted his formula as the basis for calculating circuit facilities.