duanne, This test is being performed to simulate the effect of a power line falling on a phone line. This is a problem common to Canada and the United States due to the means in which are power and telephone lines are carried to the end user. The presumed effect is that when the circuit in the product does not react safely heat and energy are likely to be conducted in such a way as to cause fire or smoke that could lead to a house fire or injury. It was not applied to modems as they used UL 478 and then later the 1st and second editions of UL 1950. When the harmonized version of UL 1950 came out(3rd edition) UL1459 requirements were rolled into it and this effective snared all CPE telco equipment manufacturers.You will need to calculate the limits of the circuit and probably change a components value. Sometimes the components in the circuit need to be reversed. This is a safety issue and not a FCC Part 68 issue. It is occassionally common for the 2 requirements to be incompatible on an initial design test run. You need to determine if the standard that is being applied is UL1950 3rd edition with UL 1459 test procedures or UL1459 itself.
In November and December there was on TREG a long series of discussions on UL 1950 overvoltage tests which covered a lot of the ground you are referring too. Regards G. Rae Dulmage, B. Comm., President TelApprove Services Corporation (613) 257 3015 Duane J. Marcroft wrote: > > Hi Treg'rs > > I don't have a copy of UL 1459 and I'm having a problem trying to > understand why a particular UL test is being performed. Could I impose on > someone to explain what UL1459,59.5,b),1) is testing and why? > > The test is being performed on a modem DAA by a piece of automated > equipment. As a consequence the person performing the test is unable to > explain much about the test. > > The TIP & RING circuit being tested consists of a 300V Sidactor, two 4.7 > ohm resistors and a RJ-11. The resistors are series with T/P and are there > to limit current when Sidactor hits break-over point. > > The UL test is applying a longitudinal 600V @ 40A to TIP and RING via the > RJ-11, with modem on-hook. There is no current limiting in the test > equipment except a fuse. > > Heres whats happening: > > When the test is run the Sidactor, one of the resistors fails and current > limit fuse in test equipment blows. But, the DAA circuit does pass the > Part 68 transient test. > > Is this a valid test? I have designed many modems and never had to pass > this test before. Can someone please advise? > > Thank you in advance. > > Duane Marcroft > Telecom Consultant
