Date: Fri, 06 Mar 1998 19:24:16 -0800 (PST) From: Simon Shapiro <shimon@simon-shapiro.org> To: Chuck Robey <chuckr@glue.umd.edu> Cc: lada@ws2301.gud.siemens.at, hackers@FreeBSD.ORG, julian@whistle.com, wilko@yedi.iaf.nl, dmlb@ragnet.demon.co.uk, Terry Lambert <tlambert@primenet.com>, Karl Denninger <karl@mcs.net> Subject: Re: SCSI Bus redundancy... Message-ID: <XFMail.980306192416.shimon@simon-shapiro.org> In-Reply-To: <Pine.BSF.3.96.980306214647.438u-100000@localhost>
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On 07-Mar-98 Chuck Robey wrote: > 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. My hardware people inform me that virtually all Telcos, domestic and international do not allow ANY AC equipment installed. I can belive test equipment is A/C, but test equipment is not permanently attached, rack-mounted. > 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). We used to run many painful practical jokes with these. I used to powe an old tube HiFi amplifier with a collection of these. BTW, some Telcos now allow A/C equipment in the rack, but not as part of their network. Network equipment must be DC, AFAIK. Simon Note: What has that got to do with FreeBSD? Quite a bit if you want to install a server in a switch... To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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