Telco equipment owned by a telco service provider is typically not required to be "Listed" or "Recognized" to a UL standard unless it resides at the customer premise (per Bellcore GR-1089-CORE). Ameritech also requires all of its equipment to be Listed or Recognized regardless of location.
By the nature of the "standard form factors" used by the telco providers (i.e. T400, T200, E220, D4, D5, SLC 2000, SLC 96, BR1/10, etc.) it is in many cases impossible to meet the creepage and clearance requirements of UL 1950 3rd Ed., EN60950, AS/NZ 3260, IEC 950 etc. It is also not possible to meet the voltage requirements for TNV in section 6 of these standards on many products especially span powering/powered products. These span powering/powered products such as ISDN, HDSL, T1, have voltages between conductors of between -200 and +130 VDC continuous. UL 1950 3rd Edition only allows up to 60 VDC. The other standards only allow up to 120 VDC. Also telco owned equipment does not necessarily isolate the telco interface from the -48VDC battery voltage or other low voltage circuitry. This is also not allowed under any of the derivations of IEC 950/UL1950. Therefore, UL 1459 is the ONLY safety standard which much of this equipment can be evaluated to. UL-1459 does not impose creepage or clearance distances, but rather uses a dielectric test. It is not uncommon for trace spacings to be less than .25mm in telco equipment and still pass the 1000V dielectric test(not that I would recommend that). UL 1950 might require trace spacings of several mm and an earlier E-mail from someone suggested 6.0 mm. I'm stumped as to how much of the telco owned equipment will be able to be listed after 2000 when UL-1459 goes away. With the telcos wanting to go farther with higher speed data, the only way to get it any distance is by using span powered range extention products which are span powered. Therefore voltages exceeding the 60 VDC limit must be used. In addition, the telcos are not going to remove or throw away billions of dollars worth of channel banks and equipment shelves simply due to a change in safety standards. I guess we'll let Bellcore, UL and the telcos figure out how to handle this mess. Jim James Wiese Regulatory Compliance Engineer ADTRAN, Inc. 205-963-8431 205-963-8250 FAX jim.wi...@adtran.com >---------- >From: Jon D Curtis[SMTP:j...@world.std.com] >Sent: Tuesday, January 27, 1998 8:56 AM >To: t...@world.std.com >Subject: BOUNCE t...@world.std.com: Non-member submission from ["bob" ><cbo...@email.msn.com>] (fwd) > >From: "bob" <cbo...@email.msn.com> >Subject: Re: Trace Spacings for PSTN Interfaces ... > >I agree with Vic, I would like to point out you may already >know that though, ITE has to comply with creepage and >clearances as stipulated in UL-1950 for USA and CSA-950. However, >those equipment/devices which has TNV circuits has to comply with >the UL-1459 in US and corresponding standard for Canada. And for >European countries it is covered in EN60950. There was a news >about UL being working on a unified standard which shall be >applicable to NAFTA, actually it was merger of two standards >UL-1950 and UL-1459 for USA. Could somebody supply more >information on this topic? > >In addition, there are some subclauses in UL standards, discussed >above which allow deviations until year 2000, and after that one >must adhere to tables given in these standards. Does this mean >devices built now but in service after 2000 has to meet the >requirements without deviations as of today? > >Your input shall be appreciated, Somm may not get this mail due to >the block placed by their bosses on access to this treggers >forum!!!!! > > >http://www.microvolt.com/ >Information is the key to success. >-----Original Message----- >From: Victor L. Boersma <vboer...@compuserve.com> >To: INTERNET:t...@world.std.com <t...@world.std.com> >Date: Monday, January 26, 1998 5:20 PM >Subject: Trace Spacings for PSTN Interfaces ... > > >> In other words, we aren't using the creepage/clearance >> tables of say UL-1950 3rd Ed. to determine the distances, >> or are we? > >The cost of doing independent creepage and clearance research >is prohibitive. At one time Bellcore may have done some, but I believe >that they have now accepted IEC 60950. I believe the same to be true >for most service providers in Europe and North America, hence, sticking >with UL-1950 should see you through. > >Vic > > > > > >
