ISDN Troubleshooting:
http://www.cisco.com/en/US/tech/tk801/tk379/technologies_tech_note09186a0080094bb8.shtml
http://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1917.html
http://articles.techrepublic.com.com/5100-10878_11-5798604.html
http://networking.ringofsaturn.com/Cisco/ciscoisdn.php
http://www.cisco.com/en/US/tech/tk801/tk379/technologies_tech_note09186a0080093c1a.shtml
http://www.cisco.com/en/US/tech/tk801/tk379/technologies_tech_note09186a0080094bb8.shtml
http://articles.techrepublic.com.com/5100-10878_11-5033402.html?tag=rbxccnbtr1
http://articles.techrepublic.com.com/5100-10878_11-1055603.html?tag=btxcsim