Trunk lines are converted to bandwidth. It is not possible to use 24 ntrunk lines from the carriers. Simultaneous calls are dependent on the codec used. A T1 could theoretically carry 80 calls and an E1 could carry 107 calls at g729a and can therefore accommodate 64 calls. So, an IP PBX with 160 extensions may have a contention rate of 8:1 (extensions to trunks). This would normally require 20 channels of an E1 or T1. In bandwidth terms, this equates to 380 kilobits.
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