sonusActiveCallEgressPstnPortNum 1.3.6.1.4.1.2879.2.2.2.1.3.1.21

For calls delivered to the PSTN (circuit) side, indicates the T1 port on the circuit card on which the call was delivered. For CNS10 cards, the port number will be in the range 1-12; for CNS30 cards, the port number will be in the range 1-28.