Chris, The ITU Overvoltage requirements are NOT the only overvoltage requirements and you should carefully look at CSA950/UL1950 for the overvoltage requirements in North America.
Overvoltagers can come from the effects of shared pole lines (shared between Electrical and Telephone Utilities), Fault conditions and Ligntning. If you don't know to what type of outside cabling the terminal will be connected, you've usually got to assume the worst. Ciao, Vic
