[asterisk-users] Why Aastra uses 48V whereas other IP Phones use much less, i.e. 5-12V

[Andrew Latham]

Also the 48v and higher systems can transmit the lower current further
than a low voltage with a higher current.



On 11/21/06, Julien Goodwin <asterisk-lists at studio442.com.au> wrote:
> On Tue, Nov 21, 2006 at 08:57:44PM -0500, Zeeshan Zakaria arranged a set of bits into the following:
> > Why Aastra phones use more electricity, i.e. 48VDC whereas other phones use
> > much less, e.g. Grandstream and Linksys both use only 5VDC. I first thought it
> > was because of PoE, but the ones with 5VDC also run fine on PoE. What is the
> > difference in power consumption then?
> The difference due to the different voltages would be < 1w. Many of the
> commercial phones (Aastra, Polycom, Cisco) use 48 volt power supplies
> as it lets them have a single power circuit for wall-warts and PoE
> (Standard PoE is 48 volts).
>
> Basic electrical theory (for DC) is that power == Watts, and Watts =
> Volts * Amps, so the only real difference between a 5v input and a 48v
> is that the 48v will use less current (although it might go through more
> DC-DC convertors those are highly efficient these days)
>
> Thanks,
> Julien
>
>
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.1 (GNU/Linux)
>
> iD8DBQFFY7PXBN1Ia7JOLPcRAu01AJ0UPc5dHFj/3gavruQPwD+oOXd+mgCgn/70
> 5w5Mrgn6JJcjHdMKGW1+ihA=
> =m+2o
> -----END PGP SIGNATURE-----
>
>
> _______________________________________________
> --Bandwidth and Colocation provided by Easynews.com --
>
> asterisk-users mailing list
> To UNSUBSCRIBE or update options visit:
>    http://lists.digium.com/mailman/listinfo/asterisk-users
>
>
>


-- 
---
Andrew Latham - AKA: LATHAMA (lay-th-ham-eh)
lathama at lathama.com - lathama at gmail.com
If any of the above are down we have bigger problems than my email!
Hind sight is most always 20/20 or better.
---