Date: Fri, 6 Mar 1998 21:51:41 -0500 (EST) From: Chuck Robey <chuckr@glue.umd.edu> To: Karl Denninger <karl@mcs.net> Cc: shimon@simon-shapiro.org, Terry Lambert <tlambert@primenet.com>, dmlb@ragnet.demon.co.uk, wilko@yedi.iaf.nl, julian@whistle.com, hackers@FreeBSD.ORG, lada@ws2301.gud.siemens.at Subject: Re: SCSI Bus redundancy... Message-ID: <Pine.BSF.3.96.980306214647.438u-100000@localhost> In-Reply-To: <19980306194939.58793@mcs.net>
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On Fri, 6 Mar 1998, Karl Denninger wrote: > On Fri, Mar 06, 1998 at 05:49:17PM -0800, Simon Shapiro wrote: > > Telcos run equipment on 48VDC. In most switching rooms, not only you are > > not allowed (and do not have) power grid AC, you cannot even generate it > > inside your own cabinet. Unless it's changed in the last 5 years, that's not true. The telco's test equipment is made by companies like HP, and runs on AC (not to mention the technicians stereos!). Of course they have AC in their office, and on every single equipment bay. Of course, their equipment does largely run on 48V nominal (which usually means around 55-56 V in fact, else the battery plant'd not ever get charged). Getting buzzed with 48V is nothing, even with 1500 Amps behind it, I've been bitten countless times. Ringing battery is _much_ more painful! Old style teletype, at polar +- 130V, would _really_ wake you up (thank god that was interrupted). > > Well, yeah, but I often wonder just how smart that really is. > > 48VDC might sound rather "harmless". Its not. The power levels running > around in those switching centers are high enough to make me *extremely* > careful when working around it. > > Bridge the positive and negative poles, and you'll find out what I mean. > > -- > -- > Karl Denninger (karl@MCS.Net)| MCSNet - Serving Chicagoland and Wisconsin > http://www.mcs.net/ | T1's from $600 monthly to FULL DS-3 Service > | NEW! K56Flex support on ALL modems > Voice: [+1 312 803-MCS1 x219]| EXCLUSIVE NEW FEATURE ON ALL PERSONAL ACCOUNTS > Fax: [+1 312 803-4929] | *SPAMBLOCK* Technology now included at no cost > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message > > ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@glue.umd.edu | communications topic, C programming, and Unix. 213 Lakeside Drive Apt T-1 | Greenbelt, MD 20770 | I run Journey2 and picnic, both FreeBSD (301) 220-2114 | version 3.0 current -- and great FUN! ----------------------------+----------------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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