In a message dated 9/18/2003, Dan Roman writes:
Assuming your talking about 60950 and the signal lines are SELV you only need basic insulation, not reinforced, between TNV-3 and SELV. Distance through insulation does not come into play, just the dielectric test and voltage rating of the wire in this case. Dan, Alex: Assuming the PSTN connection that Alex refers to is either TNV-1 or TNV-3, the requirement in the base EN 60950-1 standard for separation from SELV is basic insulation (or suitable alternative) as called out in clause 2.3.2. In this case there is no requirement for 0.4 mm distance through insulation. However, for clause 6.1.2.1 (separation from earth), there is an additional requirement for 0.4 mm distance that is imposed by Finland, Norway, and Sweden per Annex ZB. Note that an alternative to 0.4 mm solid insulation is to have two layers of insulation, each of which can withstand 1500 VRMS (or maybe 1.6 time this, the wording in Annex ZB is unclear). If the TNV wires are insulated and the SELV wires are also insulated, there will be two layers of insulation and this approach will be an option. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 [email protected] http://www.randolph-telecom.com
