Since last night,my CO reversed the polarity on the 4 ground start lines and guess what? The trouble is gone,you guys were right. Any land line call into one of the #'s get picked up and you can dial extensions.But now when the lines are called into by a cell phone,the same problem exists.We then temporarily switched the line to a pair gain pair which was serving a trunk ground start line which had no problems and the line in trouble now works fine with any incoming call from anywhere.The PBX is a NEC 2400.We are trying to provision some more PG pairs and transfer the lines off copper into the PG.The copper pairs are clean with no defects.Any ideas why cell phones can't dial an extension?Once again thanks for all the help.