Yup. A vacuum relay, oil-filled relay, reed relay, or a big power contactor with very large air gaps would not exibit this behaviour. The relays that do this are the compact, cheap PC mounted type that are ubiquitous in oven controllers and the like. Also, a relay switching lower voltage would probably not do this, and a relay switching lower power. -- Lawrence Lile Jim Sent by: pic microcontroller discussion list 11/04/02 05:06 PM Please respond to pic microcontroller discussion list To: PICLIST@MITVMA.MIT.EDU cc: Subject: Re: [EE]: Speeding up a relay - zero crossing detection "The key point here is, when a mechanical relay switches, the NO and NC contacts are MOMENTATILY SHORTED TOGETHER." I guess this would be *true* for a relay used in an open-to-the-air environment where a PLASMA forms (from the 'sparcing' in the air which then is conductive) between the contacts - - as opposed to the use of a vacuum relay which should not be subject to such a phenomonon? RF Jim -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.