Here is a unique item to add to your system admin toolbox. At times it is necessary to know what the phone number is for a phone jack. IE: modem dial in. The following phone number when typed in will give an automated response that tells you the phone number of that line. As well when you hang up it will dial the number to validate that the line is working. I know this number is ok for Canada, however please drop a note on this thread if you are from the USA and let everyone know if valid.
1 888-837-8274