If memory serves me correctly, there ought to be
several 8pin ring detector chips available.  Some
years ago, Radio Shack even carried one.  I don't
have any of my telcom data books here, but I sure
I could do a search on CAPS and find some.  I hope
you weren't trying to use a PIC just as a ring
detector.

-Harrison Cooper
hcooper@corp.es.com