asterisk users - Oct 2012 - How can read the headers ISDN?

Hello all,
My name is Danilo and I have a problem with the ISDN. I hope I have the 
wrong section. =P
I have a CS1000 Nortel central with release 5.50. This central is 
attached to an Asterisk server with Sangoma PRI ISDN.
I need to read the headers of ISDN and comes running from Nortel to 
Asterisk. How can I read them?

Thank you,
Danilo.

--