The calculator helps to convert telecommunications traffic into Erlang for given total call duration for a period of time.
Erlang - telecommunications traffic measurement unit, it was named in honour of Dutch mathematician A. K. Erlang, who developed telecommunications traffic theory. An Erlang represents the continuous use of one voice path. In practice, it is used to describe the total traffic volume of one hour.
When you have telephone call during half an hour and then idle another half an hour you produce 0.5 erlang telecom traffic. When you and your friend simultaneously call someone and talk during one hour, your total traffic load will be 2 erlangs.