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number of users – given channels

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    I’m searching for some kind of a document in which a given number of voice channels are compared with the number of provided users.
    E.g. 2 channels are good for 15 people…
    Of course this depends on what the office is doing, an call centre with 15 employees will need more then lets say a baker 🙂
    I need some rough information, which will cover most cases.

    Thanx a lot!




    I dont have any document like that you required, but will try to give some information about this matter.

    If you have the given number of voice channels (N), you should choice your preferred blocking probability (GOS, range from 1%-4%). From these values of N and GOS, based on Erlang table or Erlang calculator you will get the traffic capability in Erlang (E).

    Then you have know the average time (in minutes) that each subscriber occupies the voice channel per hour (T), by mean of forecasting or statistical data. Hence you can determine the average traffic for each subscriber (Es) by the following formula: Es=T/60. And at last, you will get the number of subscriber = E/Es.

    Below is the example for easy understanding:

    Let say N = 30 channels, GOS = 2% -> E = 22 Erlang.

    Let say T = 1.5 minutes -> Es = 1.5/60 = 0.025 Erlang.

    -> Number of subscriber = 22/0.025 = 880 subscribers.


    Balakrishnan S Naicker

    Hi Misa,
    I went through your explanation. Still I did not understand what does “traffic” means??
    Please let me whether my understanding is correct

    Say the number of subscriber lines connected to a switch is = 10 and
    average holding time of each subscriber line is =2 minutes.

    Total traffic = 10 * 2 = 20 minutes.

    Please correct me, if I am wrong.


    hi misa,

    thank you for your information 🙂

    One Question to your “T” to be sure I understand you right:

    Is T the average duration time of a call at this site? – ’cause this is something I can presume from similar sites.
    Or is T something different I’ve just not understood yet?


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