If one circuit receives 50 calls and each call lasts 45 seconds, how much of that circuit is being used in Erlang?

A. 0.5

B. 6.25

C. 0.625

D. 62.5

E. 0.18

Answer: c) 0.625 Erl

Explanation:

The Erlang, is an adimensional quantity that compute how occupied is a telephony circuit, taking which is called the "Busy Hour Traffic", which is the time when the circuit is most stressed by the users trying to make calls.

If we take 1 hour = 3600 sec, if we would have exactly 60 calls of exactly 60 sec of duration each, we would have the circuit busy 100% time, and the traffic intensity would be exactly 1 Erlang.

If. in the same hour of 3600 sec, we have 50 calls, and each call lasts 45 seconds, it is clear that the circuit will be idle for some time.

We can compute the percentage that the circuit will be busy, in Erlangs, using the following equation:

Traffic Intensity = 50 (call/Hr). 45 (sec/call). 1 (hr/3600 sec) = 0.625 Erl