I have a DS1 circuit that is down and I am trying to trouble shoot. It is a TN464F board configured as ISDN-PRI. The D channel in the Signal Group is in service. My question is this, when I connect a loopback plug to the integrated CSU for that circuit should the circuit show In Service when I status the trunk group? Since the data transmitted is looped to the receive pair the board should see this as a live circuit, correct or no?