Lesson 7: A More Complex Call Center

Our call center is quite simple. Though our next example is still fairly simple, let’s consider some additional issues such as the number of phones lines available, how long a customer is willing to wait on hold, alternate routings and additional action logic.

Another Call Center

Download Lesson 7 – Call Center model here.

Open the Lesson 7 – Call Center model.

Let’s look at what attributes and variables are being used in this model.

Click the Insert menu and select Attributes & Variables.

Attribute and Variable Windows in ProcessModel



Complexity – A descriptive attribute describing how difficult the call is

Tolerance – How long a customer is willing to wait on hold before hanging up (reneging)

Start_Hold_Time – The simulation clock time when the customer was first put on hold


In_Process – The number of calls pending a resolution

On_Hold – The number of callers currently on hold

Abandons – The number of callers who hung up before being helped

Hold_Time – The hold time of each call

Research_Cycle_Time – The total amount of cycle time a Research call was in the system


  1. How many trunk lines are there?
  2. What is the purpose of the route coming out of the bottom of the Return Call activity?
  3. How many TSR1 operators are there?
  4. How many TSR2 operators are there?
  5. Is TSR1 helping TSR2, or is TSR2 helping TSR1?
  6. Where do the Renege calls go?

Action Logic Window

The action logic window is big and provides sufficient screen space to read and review the logic. Click on the action tab in the properties dialog, after selecting the arrival route to open the action logic window.

Double click the arrival route. Click the Action tab.


The number of in-process calls is incremented each time a new entity arrives. The call complexity is set using a user-defined distribution to one of three settings: easy, moderate, or difficult. The caller’s tolerance to stay on hold is set using a triangular distribution.

Double click the route between Take Call and Research Problem. Click the Action tab.


The Trunc_Line resource is freed since the caller has hung up and research will be starting in order to resolve the issue.

At any given location in your model, you can GET and/or FREE resources using connector lines or using action logic, but not both. For example, you may use connector lines at one activity and action logic at another activity. But you can’t use both methods at the same activity.

Double click the Research Problem activity. Click the Action tab.


All moderate calls will take a time determined by the Uniform distribution U(20,10). All other calls (difficult) will use a time assigned using the T(1.0,1.5,3.0) distribution. Remember the time on the General tab is 0 since the time is specified in the action logic.


7. With so many distributions in this model, how can you ensure that you have a good statistical representation of realistic results?

Self Teaching Guide

Getting Started


  1. Your First Model
  2. Replications and Distributions
  3. Entity Arrivals
  4. Routings
  5. Attributes, Variables, and Action Logic
  6. Shifts
  7. A More Complex Call Center
  8. Model Building Techniques

Case Studies

  1. Analysis
  2. Replications
  3. Froedtert Hospital Improves ICU Care
  4. Nuclear Site Cleanup
  5. Restaurant Customer Seating Optimization

Appendix: Answers to Lesson Questions

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