In a message dated 1/2/01, Gaétan Hogue writes:
> I have an TNV-1 interface (ISDN) on a card going in a computer. > Some of my designers told me that we need reinforced isolation > transformer(3kv) in Norway. > Hi Gaétan: The main requirement for reinforced insulation is between the TNV-1 circuit and the AC power mains. This is usually taken care of by the insulation in your power supply. Your designers may be referring to the requirement for supplementary insulation between TNV-1 circuits and earth ground. In the main text of EN 60950, only a hipot test is required (clause 6.4.1), but Annex ZB in EN 60950 calls out additional requirements for Norway and Sweden. For Norway, you will need supplementary insulation unless you qualify for the exemptions related to permanent grounding or a Type B mains plug. If you decide to implement supplementary insulation, keep in mind that in addition to a 1500 VRMS hipot test, there are specific requirements for creepage distance, clearance distance, and distance through insulation. This will affect your board layout, your choice of transformer, and (sometimes) your choice of connector. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com
