In a message dated 10/21/2002, Paul Denomme writes:
> I am currently working on a design for the telecom industry. I need to > determine the minimum specifications for setting up my design rules for > both internal and external layers and connector selection. According to > UL60950 table 2N the minimum clearance that I need to adhere to is .2mm > (voltages up to and including 125 V r.m.s or DC). This translates to a > .008" clearance. Will this be acceptable? > Hi Paul: If your circuits interface to telephone lines, you first need to determine whether the type of circuit is TNV-1, TNV-2, or TNV-3, per clause 2.3.1 of UL 60950, Third Edition. Once you classify the circuit, other clauses that may apply include 2.3.2 and all of clause 6. In general, creepage and clearance distances for separating telecom circuits from SELV and from earth ground are somewhat larger than what you mention above, but the specific requirements that apply depend on the TNV classification and on the equipment installation. If you can provide more details either to the group or to me offline, I would be happy to try and give you more specific answers to your questions. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com
