From owner-freebsd-hackers Mon Dec 20 11:49:55 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by hub.freebsd.org (Postfix) with ESMTP id 4B21014A1F for ; Mon, 20 Dec 1999 11:49:53 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id LAA16719; Mon, 20 Dec 1999 11:49:45 -0800 (PST) (envelope-from dillon) Date: Mon, 20 Dec 1999 11:49:45 -0800 (PST) From: Matthew Dillon Message-Id: <199912201949.LAA16719@apollo.backplane.com> To: Wes Peters Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Cool little 100BaseTX switch - they're coming down in price References: <199912190410.UAA01049@apollo.backplane.com> <385C60FC.7613CB55@bellatlantic.net> <19991218225758.A23729@futuresouth.com> <199912190556.AAA08484@whizzo.transsys.com> <199912191943.LAA06826@apollo.backplane.com> <385D47D3.FCEE9EAB@softweyr.com> <199912192127.NAA09156@apollo.backplane.com> <385DDE7A.1A0ED466@softweyr.com> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :> :"everyone" here). :> :> This is not true at all. : :Oh, and how many products have you passed through FCC/EC/Japanese environmental :certification? None, apparently. Four in the last 15 years. I've been involved with in-home electronic management systems and believe me, all that shit needs FCC and UL. :> supply inside verses depending on a DC adapter does not make FCC cert. :> more difficult. : :You're wrong. It nearly always requires adding some sort of faraday cage :around the power supply, and often around the entire enclosure due to the :difficulty in isolating the 60 Hz harmonics within the power supply in :small equipment. For a small, cheap hub or switch this just kills the : :Wes Peters Softweyr LLC :wes@softweyr.com http://softweyr.com/ This is old news - modern switching power supplies (and we are talking basically a chip, an inductor, and two big caps here) switch at 50 KHz or higher, which makes things a whole lot easier. No 60Hz humm, no vibration - hell, you can even run the frequency up past 100 MHz and not hear a peep out of it. Modern switching power supply chips also have most of the shutdown circuitry required, including temperature and current limiting, slow-start, and other features. Add in few small caps or perhaps a ferrite bead or two to filter out HF on the DC output and you are all done. Whoopie. Whoopie. The only time we've ever needed a faraday cage has been in a cable network unit for a hotel, and the video switching channels for the in-home unit - to protect sensitive RF circuitry from the rest of the world. If there is a specific reason you believe that putting a small switching supply inside the box requires extra FCC work, I'm all ears. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message