Em 11/3/2012 13:03, Spehro Pefhany escreveu: > At 11:31 AM 3/11/2012, you wrote: >> On Fri, Mar 9, 2012 at 12:58 PM, Herbert Graf wrote: >> >>> "Integrated Magnetics" has nothing to do primarily with noise >>> suppression. Ethernet requires a transformer between the MAC and the >>> actual jack. >>> >>> Traditionally this was always done by an external part. Look at pretty >>> much any network card and chances are you'll see the transformer, it's >>> easy to spot. >>> >>> To reduce costs, manus started putting the "magnetics" into the jack >>> itself. This results in a slightly larger jack, but one less part to >>> source, route for and mount. >> My wife, also a computer "geek" but without an EE inclination was asking >> me why anyone would design with a jack without built-in magnetics these >> days. >> >> Could anyone clue me in? >> >> Thanks, >> Bill > To save a bit of money. The combination of an external transformer and a > passive jack is still a bit less costly (used to be a LOT less costly, > but the integrated ones have come down a lot in cost). Putting it in the > can costs more and probably involves as much _total_ labor but saves on > the footprint and PCB assembly costs. > > Of course there are also plenty of applications for RJ45 jacks that don't > involve Ethernet. Power Over Ethernet requires access to the center tap of the primary the transformer. AFAIK the jacks with integrated transformers don't expose the primary center taps. Isaac --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .