From: Dan Roman <[email protected]> Reply-To: [email protected] Organization: Dialogic Corporation X-Mailer: Mozilla 3.0Gold (WinNT; I) Mime-Version: 1.0 To: [email protected] Subject: Re: Printed Circuit Board Layout References: <[email protected]> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit
Doug, There seem to be some confusing responses being returned to you. I'll offer one more response but I suggest you contact the lab (UL I assume) that is going to be doing the testing for you before you etch the boards! Throughout most of the world E1 is considered SELV so the quotes you received for supplementary insulation @ 240 Vac, 2.5 mm between TNV and SELV or Earth and 1500 V dielectric, only apply to loop/ground start interfaces and not to a "digital" interface like yours. Having said that, T1 interfaces come in two flavors, DSX-1 and DS1. DSX-1 is SELV, "short haul", supposed to be behind a registered CSU (which gives the safety protection), in-building wiring. DS1 has the CSU built-in and is TNV, "long haul", goes outside of the building on the pole or underground with the AC wiring. My experience with UL has been that DSX-1 is treated like SELV (no testing) and DS1 like TNV which requires overvoltage testing, dielectrics, and creepage and clearance. I believe also that UL's requirement is basic insulation between TNV and SELV or Earth which still means 1500 V dielectric but only 1.6 mm creepage and clearance but it has been quite awhile since I did a CSU application so as I said, check with them first. BTW, they have no requirement for T/R or T1/R1 spacing and for EMI purposes I would route each tip and ring pair as closely as possible to each other (they are differential signals after all).
