DPC stands for 'destination point code'. In simple terms, the DPC defines the group of timeslots that your outgoing calls are directed to. In most cases, your DPC will be the exchange's point code.
OPC stands for 'originating point code'. In simple terms, the OPC defines the group of timeslots from where your outgoing calls originate. In most cases, your exchange will tell you that 'your point code is?' when you register with them. This point code will be your OPC.
When the exchange provides you with a point code, it will be in one of two forms;
The correct form to use when configuring the Aculab firmware is the decimal form.
If you are given a point code in the Network-Cluster-Member form you will have to convert it to the Decimal form to ensure the firmware is configured correctly. Please see 'How do I perform point code conversion for SS7?' for further details.
Configuring point codes incorrectly will result in an inactive (bad) Layer 2.