Serial line troubleshooting: http://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1915.html http://www.cisco.com/application/pdf/paws/14170/T1_alarms.pdf http://www.cisco.com/en/US/tech/tk713/tk628/technologies_tech_note09186a00801069ff.shtml http://www.n-cg.net/ncgpdf/T1-Troubleshooting.pdf http://www-china.cisco.com/en/US/tech/tk713/tk628/technologies_tech_note09186a0080104552.shtml