> For TNV-1 under E1 there is no category of outside wiring All E1 > circuits connect to inside wiring to NTTP (network terminating ponit)
The overvoltage requirements in UL1950, CSA950 and IEC60950 were introduced because of the fact that in North America the outside wiring is strung on the same poles as the electrical supply. If due to ice storms and hurricanes etc. the electrical wiring falls down and falls on the telephone wiring, you may cause an overvoltage on the equipment that terminates the telephone cable. (There are scientific studies that show the probabilities of this happening, how long before the fuses will pop in the high voltage line etc., etc.) Most countries that use E1 service enjoy buried cabling, where the electrical wire is not likely to fall on the telephone cable, etc., etc...................................... Wouldn't it be nice if there were a requirement that for each clause in a standard, the rationale for the test be given ? Ciao, Vic
