Increment: Increment is deducted when the call is established for.
Initial increment: Initial increment is deducted when the call is still connected after 1 sec also.
Admin will add the seconds in increment and initial increment as per the requirement in origination rates, as shown in the below screenshot:

Menu Location : Tariff→ Origination Rates

If one will dial a number, when the call is established for 1 sec it will deduct the cost by increment and after the on-going call, after every 60 sec gap it will deduct from initial increment.
Let’s take one example for the same, how it will deduct the rates as per the seconds mentioned in increment and initial increment .

Below is the configuration of origination rate
Cost per minute= 1
Initial Increment= 1
Increment = 60
Rest of the value will assume 0

Customer established a call, on 1 sec the system will generate debit = 1/60 = 0.0167, Where 60 seconds is increment.
Then for 2 sec to 60 sec = 1 rs (that is for 60 sec ) + 0.0167 (that is for 1 sec) = 1.0167
Then for 61 sec to 120 sec = 1 + 1 + 0.0167 = 2.0167
For further reference you can see the below screenshot.

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