<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">You can get DC-DC convertors that do this.<div><br></div><div>You need to be careful because exchanges are negative 48 volts (relative to ground) whereas most of the DC converters you will find are positive 48 volts.</div><div><br></div><div>For added smarts you can use a bridge rectifier to take your A and B feeds via the AC inputs and run the converter from the negative leg of the bridge.</div><div><br></div><div>I've seen this done at Nextgen to run an out of band modem....<br><div> <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" style="font: normal normal normal 12px/normal Helvetica; "><br class="Apple-interchange-newline">--</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" style="font: normal normal normal 12px/normal Helvetica; ">John Lindsay - Carrier Relations Manager - Internode and Agile</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" style="font: normal normal normal 12px/normal Helvetica; ">Street: Level 3, 150 Grenfell St, Adelaide, South Australia</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" style="font: normal normal normal 12px/normal Helvetica; ">Postal: P.O. Box 284, Rundle Mall, Adelaide, S.A. 5000</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" style="font: normal normal normal 12px/normal Helvetica; ">Direct: ph +61 8 8228 2965 - fx +61 8 8235 6965 mb +61 4 0357 7711</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" style="font: normal normal normal 12px/normal Helvetica; ">Switch: ph +61 8 8228 2999 - fx +61 8 8235 6999</font></div><div><br class="webkit-block-placeholder"></div></span><br class="Apple-interchange-newline"> </div><br><div><div>On 05/09/2008, at 11:17 AM, Brent Paddon wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Arial; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><div bgcolor="#ffffff" text="#000000">Many years ago when analogue modems ruled the world, I had a local transformer company create a handful<br>of transformers to take in 240v AC and put out 30x 20v AC to feed some modem banks.<br><br>Different for you, but for someone with some electronics knowledge I wouldn't imagine it would be too hard to<br>bring 48v down to 12v DC for a modem which ran on that...<span class="Apple-converted-space"> </span><br><br>/brent<br><pre class="moz-signature" cols="72">Brent Paddon
Director | Over the Wire Pty Ltd
<a class="moz-txt-link-abbreviated" href="mailto:brent.paddon@overthewire.com.au" style="color: blue; text-decoration: underline; ">brent.paddon@overthewire.com.au</a> | <a class="moz-txt-link-abbreviated" href="http://www.overthewire.com.au" style="color: blue; text-decoration: underline; ">www.overthewire.com.au</a>
Phone: 07 3847 9292 | Fax: 07 3847 9696 | Mobile: 0400 2400 54 | Direct: 07 3503 4807</pre><br><br>Chris Pollock wrote:<blockquote cite="mid:001a01c90ef8$97332700$c5997500$@com.au" type="cite"><div class="Section1"><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Hi,<o:p></o:p></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">I have an application for some dial-up modems for out of band management but the only power available is 48v DC. Does anyone have a line on any reasonably priced serial dial-up modems, or perhaps a dc/dc converter or what have you that would let them run off 48vDC? The ones I’ve found have all been industrial-strength hardened type stuff and clocking in at $700+ which is just not practical.<o:p></o:p></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Any ideas? On or off list replies are welcome.<o:p></o:p></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Thanks,<o:p></o:p></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-US">--<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Chris Pollock,<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Network Manager,<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Demand Broadband.<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-US">e.<span class="Apple-converted-space"> </span><a class="moz-txt-link-abbreviated" href="mailto:chris@demand.com.au" style="color: blue; text-decoration: underline; ">chris@demand.com.au</a><o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-US">p. 1300 767 445<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-US">f. 1300 767 556<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-US">m. 0410 747 765<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><span lang="EN-US">skype. christopherpollock<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div></div><pre wrap=""><hr size="4" width="90%">_______________________________________________
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