Trunk Facilities Calculator
Note: The calculator is a Java program. If it does not appear below after a minute or so, you may not have a Java-enabled browser or Java may not be enabled on your browser. Check to make sure it is enabled. Instructions for using the calculator are displayed below.
Press your browser's refresh or re-load button to clear the fields.
Offered Calls for Peak Interval- This value represents the number of calls you expect to receive within the peak interval (i.e. the period during the day with the largest call volume).
Desired Grade of Service- This figure represents your target blockage (that is, the percentage of callers that will receive a busy due to no trunks being available). For example, if you desire a target blockage of 1%, you would enter 0.01 here (convert your percentage to decimal by dividing by 100 -- for 1%, take 1 and divide by 100 to arrive at 0.01).
Number of Minutes in Peak Interval- This value specifies the length of the peak interval in minutes. For example, if your call accounting system reports in half hour intervals, you would enter 30 here. For one hour interval periods, enter 60.
Average Length of Call in Seconds- To determine the average amount of time a trunk will be used per call, you will need to know the average length of that call in seconds. Please note that this is talk time only, and does not include any post-processing time (i.e. only specify the time that the trunk is in use by the call).
Enter # of trunks available to see what the blockage will be-->- This button allows you to see what the blockage/grade of service will be if the number of trunks you have available differs from the value specified by the calculator. For example, suppose the calculator says you need 51 trunks in order to have a 0.5% blockage or grade of service. Let's assume you only have 49 trunks available and you want to see what the blockage will be with 49 trunks and all else being equal. Simply enter 49 in the text box to the right of this button, then press the button. The calculator will return the blockage for 49 trunks. In general, press this button when you want to see what the results will be if you have a specific number of trunks in mind, and press the other button when you want to see how many trunks you will need. This button ignores the Desired Grade Of Service provided, because that is what is calculated here. However, it does not ignore the remaining values provided, because it needs them to determine the results.
How This Program Works
This program contains an algorithm known as Erlang B, which calculates the trunk facilities requirements of a center by using random distribution patterns based on random bursts of call arrivals. Erlang B assumes that any callers that receive a busy due to trunk blockage will hang up and not retry the call. Under normal conditions, at least some of the callers will usually retry the call, so the grade of service returned by the program may be lower (i.e. better) than that in real life. However, the algorithm does provides a good accurate model with which to work. Another algorithm used mainly in European centers is the Poisson algorithm, which, like Erlang B, determines trunk facilities requirements. Unlike Erlang B, however, it assumes that all callers receiving a busy will try calling again at random times in order to get through. The actual number of callers that will retry their call will actually be somewhere between 0% (Erlang B) and 100% (Poisson), so Poisson will actually over-estimate the trunk requirements slightly.
The Trunk Facilities Calculator has been extensively tested in conjunction with professionally available call center simulation packages and has found to be accurate in its results. However, PREFERRED SOLUTIONS MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE WORKFORCE CALCULATOR, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. PREFERRED SOLUTIONS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING THIS SOFTWARE OR ITS DERIVATIVES.
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