How many lines do I need to provide on a trunk group that will be offered 5.5 Erlangs of traffic during its busy hour if I am prepared to accept that 3 calls in 100 will be blocked and that half of those blocked calls will immediately be retried?
An example calculation
To find the answer to this question, follow these steps:
• | Select the Extended Erlang B Calculator using the tab control at the top of the window. |
• | Click on the radio button marked Unknown that is in the Lines section of the calculator. This indicates that you wish to calculate the lines variable. |
• | Enter the figure 50 into the edit box in the Recall factor section of the calculator. |
• | Enter the figure 5.5 into the edit box in the B.H.T. section of the calculator. |
• | Enter the figure 0.03 into the edit box in the Blocking section of the calculator. |
• | Press the Calculate button. |
After a short time, the figure 11 will be displayed in the Lines edit box indicating that 11 lines will be required to carry 5.5 Erlangs of traffic with a blocking figure of 3% if the assumptions associated with the Extended Erlang B traffic model are met and if 50% of blocked calls are retried.