asterisk users - May 2007 - standard TDM interface cards that work in Asterisk?

Hi:

Does anybody know of a TDM interface card for *digital Centrex* that
will work in Asterisk? We're not talking about BRI, here -- the lines
have Nortel digital sets on them, and we want to run them into an
Asterisk PBX.

Centrex is more widely used in NAm.

-Stephen-