Hi Moshe, I thought that if you were going to shunt any overvoltage to ground it had to be permanently earthed per IEC950 4'th ammendement?.
Consider this scenario...You have some TNV type box (PBX etc.) supplied by a PSU using the earth ground on the power plug. A user unplugs the device and it is assumed to be reasonably safe, however you still have your off premise TNV connection made. Now you have an overvoltage and the ungrounded metal chasis becomes live. In your case, you say there is no connection to ground in the first place. Let me know what you think. It would be my understanding that the scenario you propose would not be permitted. Regards, Hugh Long At 11:30 PM 11/10/98 +0200, you wrote: >Moshe Hello! > >Let me re-phrase your question. You are asking is a transient >voltage suppressor can bridge "basic insulation" between a TNV-3 >circuit as defined in UL1950/EN60950 and an unearthed chassis? > >Personally, I believe this is OK for North America (if you are using >a Recognized suppressor suitable for the ratings). However, this >could cause problems for Europe where spark gaps are preferred. > >Before you implement the design of your telephone interface, I >suggest you consult with the appropriate Third Party Safety/EMC >Telecoms Certification Agencies who will eventually test and >Approve your equipment. > > > > > >> Hello everyone, >> >> In a telecommunication device I need to connect a transient suppressor from the phone line >> to the metal chassis, which is not safety grounded. (I believe this is defined a class II >> device). >> Are there any special considerations / limitations in this condition? >> >> thanks in advance, >> moshe >> >>d >> > > >PETER S. MERGUERIAN >MANAGING DIRECTOR >PRODUCT TESTING DIVISION >I.T.L. (PRODUCT TESTING) LTD. >HACHAROSHET 26, P.O.B. 211 >OR YEHUDA 60251, ISRAEL > >TEL: 972-3-5339022 >FAX: 972-3-5339019 >E-MAIL: [email protected] >Visit our Website: http://www.itl.co.il > > Hugh Long, Senior Designer Design Integrity Cadence Design Systems (Canada) Ltd. 1130 Morrison Drive Suite 310 Ottawa, Ontario K2H 9N6 Phone: 613-726-2753 Fax: 613-828-0528 [email protected]
