Dear People, Well, I'll be the first to say it - I must be the dumbest person around.
After having several very patient souls email me off-line with suggestions I'm still in a quandary. That is absolutely no reflection on these good people. If my product connects to a dry T1 line, the signals on the T1 line are 3 volt signals. I have a very technical report detailing results from the signal mask. In some cases, the report even specifies milli-volts. All digital. No analog. Someone did mention (off-line) that the US views the T1 line as SELV with the capability of hitting 150 volts. So, you go to Table 6, UL-1950 and lo n' behold you get 1.6 mm for Basic. That's (TIP or RING) -> GND and (TIP or RING) -> the other side of the line isolation transformer. Imposing SELV Basic insulation requirements thus causes testing to be done at 1,000 volts (Table 18). He went on to say that Europe considers the E1 line as NOT SELV with the capability of hitting 250 volts. They impose primary voltage standards. Thus, you go over to Table 6, EN-60950 and lo n' behold you get 2.5 mm. BUT, that's only for That's (TIP or RING) -> GND. Spacing to traces on the other side of the line isolation transformer are doubled for reinforced insulation and that is 5.0mm. Imposing primary voltage requirements thus causes testing to be done at 3,000 volts (also Table 18). Both standards agree of 0.4mm for inner layers. Now, standards and requirements for primary and secondary traces outside of telco? No problem. But, I'll be damned if I can get someone to tell me (no insult intended to anyone - maybe it's my stupidity) the rationalization to "working voltage" of the T1 or E1 line that gets me some resolution to Table 6 in either standard. And I'll be damned again if I can find anything in my UL, FCC or CTR reports or standards that mention anything close to 150 volts for domestic stuff or 250 volts for European. Didn't mean to offend anyone that has helped so far. The discussion both on and off line has been an eye opener. Just very frustrated. I'm trying to define and write up some agency design criteria for engineering. And don't be afraid to email me off-line, either. mailto:dmck...@paragon-networks.com Regards, Doug
