Troubleshooting ISDN can be a tricky process. In some cases, now a days, you will have an external NT-1 . This is great, because it will usually have lights to help aid in the process. The switch protocol light will be good if you have the correct switch protocol selected on your video conference equipment. Plus, you also want to look for the SPID/number lights(S1,S2,P1,P2 or something of that nature.) . These lights will help you to determine if you have entered the correct spid and phone numbers on your video conference equipment.

Most of the time, your video conference equipment will have a easy to configure interface. Through the main screen there should be a section for ISDN settings. You will have to look around, as it is in a different place on different equipment. However, the general terms that are used to describe the settings are going to be similar on most devices. For the switch protocol your almost always going to be selecting National ISDN 1 . AT&T 5ESS is still in use in some areas of Europe or other parts of the world. The spid format is usually the same. But, if you run into trouble contact your provider. For National ISDN 1 the SPIDs are almost always going to be the complete phone number followed by 0101 . So for example, S1 55555555540101 and S2 5555555550101 . P1 and P2 or phone numbers being 555555554 and 5555555555 . In the case of AT&T 5ESS it will usually start with or end with just 01 . Again, the provider should have given you all of this information or it couldn't hurt to contact them. As with most computer equipment, if you have trouble try rebooting and/or power cycling everything, including the external NT-1 box. Also, try switching the numbers around you may have them in the wrong order, even if it does not seem like it.