I currently have a setup with a PTP T-1 and some DCD boards. The data side is passed through the T-1 card via the amphenol cable to a V.35 connection. Now the customer needs to change the routers, and the new ones only have RJ-45 connectors. What would be the best way to do this? could we install INA boards and by pass the built in router feature and just pass the info along to the external router?

Are you saying the new routers don't have a serial interface? If so you will need a drop and insert CSU/DSU to split the channels.

the new routers are using an RJ-45 connection. Any recommendations on a CSU/DSU unit?

What is the interface? T-1 DSX? Do the routers have an extra port to add a DSX back to the PBX? What make/model?

the routers are not equipped with anything to give back channels to the PBX, as far as I know. I will check on the model number.