This article reports the stages of evaluating the requirements of a call centre and the number of trunks (central office lines) necessary to handle incoming calls.
Description of the design process
To start a call center design first of all you should determine two main things:
1. How many call centre operators do I need?
2. How many trunks do I need?
Because call holding time depends on average queuing time (that depends on the quantity of agents available), these two questions must be addressed in the order shown.
How many agents do I need?
Defining the number of agents necessary is a long process which will require regular revaluation in case if the situation changes. Revaluation can be done for each working hour of a day, and should include such factors as marketing campaigns and daily call peaks.
We suggest making a calculation for each working hour. In order to assess the quantity of operators necessary in a particular hour, the following information relating to that hour is required as a minimum:
1. Amount of calls received
2. Average length of these calls
3. Acceptable average level of delay that incoming callers may experience.
Items 1 and 2 relate to the incoming traffic levels and must be ascertained from call stats or from estimates based on your understanding your business. Item 3 is the criterion of your performance. Another performance criterion can be used. It determines call handling in terms of the percentage of calls answered within a target queuing time (e.g. 85% of calls answered within 20 seconds of ringing). This criterion can be more important.
Wrap up time (or wrap time) is the time the operator is unavailable to handle a call after it has been completed. Wrap up time is usually the time when the agents fulfill some administrative tasks relating to a call such as entering an order on a terminal, average call duration should comprise the wrap up time.
After establishing these three factors for an hour, estimate the number of operators necessary.
How many trunks do I need?
While the quantity of operators necessary can (and should) be dynamic, changing from hour to hour, the amount of lines necessary to connect a call center with a central office exchange is constant (at least in traditional circuit switched technology) and must serve for the maximum expected traffic levels that will be faced. Managing the number of lines necessary is known as dimensioning a trunk group.