(1878-1929) A Danish mathematician. Erlang the language and unit were named after him. Interested in the theory of probability, in 1908 Erlang joined the Copenhagen Telephone Company where he studied the problem of waiting times for telephone calls. He worked out how to calculate the fraction of callers who must wait due to all the lines of an exchange being in use. His formula for loss and waiting time was published in 1917. It is now known as the "Erlang formula" and is still in use today.