[AusNOG] dial-up modem with 48v DC power option?

[John Lindsay]

You can get DC-DC convertors that do this.

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.

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.

I've seen this done at Nextgen to run an out of band modem....

--
John Lindsay - Carrier Relations Manager - Internode and Agile
Street: Level 3, 150 Grenfell St, Adelaide, South Australia
Postal: P.O. Box 284, Rundle Mall, Adelaide, S.A. 5000
Direct: ph +61 8 8228 2965 - fx +61 8 8235 6965 mb +61 4 0357 7711
Switch: ph +61 8 8228 2999 - fx +61 8 8235 6999



On 05/09/2008, at 11:17 AM, Brent Paddon wrote:

> Many years ago when analogue modems ruled the world, I had a local  
> transformer company create a handful
> of transformers to take in 240v AC and put out 30x 20v AC to feed  
> some modem banks.
>
> Different for you, but for someone with some electronics knowledge I  
> wouldn't imagine it would be too hard to
> bring 48v down to 12v DC for a modem which ran on that...
>
> /brent
> Brent Paddon
>
> Director | Over the Wire Pty Ltd
> brent.paddon at overthewire.com.au | www.overthewire.com.au
> Phone: 07 3847 9292 | Fax: 07 3847 9696 | Mobile: 0400 2400 54 |  
> Direct: 07 3503 4807
>
>
> Chris Pollock wrote:
>>
>> Hi,
>>
>> 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.
>>
>> Any ideas?  On or off list replies are welcome.
>>
>> Thanks,
>> --
>> Chris Pollock,
>> Network Manager,
>> Demand Broadband.
>> e. chris at demand.com.au
>> p. 1300 767 445
>> f. 1300 767 556
>> m. 0410 747 765
>> skype. christopherpollock
>>
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