Engset calculator

This is similar to the Erlang B Calculator, but should be used when the number of traffic sources is finite (less than ten times the number of lines). It can be used to work out the number of voice lines which need to be engineered in a trunk group, if the busy hour traffic (in Erlangs) offered to that trunk group is known. The calculator takes two parameters: blocking is the percentage of calls which will be blocked (receive a busy signal), because an insufficient number of lines have been provided; sources is the number of sources (points of generation) from which the offered traffic originates.