ryu wrote: > > I saw the term in the IPC-610. I think it has something to do with the > design of a product for cross talk elimination. But can someone tell me > if there is a minimal or maximum requirement for the distance, is there > any number a designer needs to follow? if the answer is no, then how the > designer comes up with the number ? Thanks. Well I've been trying all day to get to look it up for context "but it's not happenin' today!". The electrically dependent clearances have to do with either noise (often crosstalk) or safety. What matters is the amount and type (i.e. switching or static) of energy and the distances (and insulators) around that energy. Crosstalk is a complex issue, and Groovy's correct in that it involves gory detail on the signals involved as in their emmissive (is this a word?) characteristics and their suscept- ability (where's my spellchecker - I'll risk flames to get the comment out today). There is not a simple calculation to get specifics (a spice/field solver problem) and it is complicated (or eased, actually) by the timing of events i.e. if the receptor is not listening at that time the aggressor can do whatever it needs to. Electrical safety depends heavily on the environment and is just as deep a calculation to arrive at "knowns" - or deeper since you nomally have non-uniform insulators (pwb, s/m, air, moisture, contaminants, etc). Both issues, however, rely on a simple fundamental principle. Like any energy, electric and magnetic fields dissapate with the rule of inverse squares. That is, the effect of one conductor on another decreases with the square of the change in distance. One unit change in distance provides one unit change in interference but 2 units distance make a 4 unit effect. So while exactitude requires too much math, the principle relies on very little. This reply is quite hurried (entire books exist on but one aspect of the many raised here) but I hope I've helped. Regards, -- Jeff Seeger Applied CAD Knowledge Inc Chief Technical Officer Tyngsboro, MA 01879 jseeger "at" appliedcad "dot" com 978 649 9800 ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################