Zeeshan Zakaria
2006-Nov-21 18:57 UTC
[asterisk-users] Why Aastra uses 48V whereas other IP Phones use much less, i.e. 5-12V
Hi, 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? -- Zeeshan A Zakaria -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20061121/08e9e4eb/attachment.htm
Julien Goodwin
2006-Nov-21 19:20 UTC
[asterisk-users] Why Aastra uses 48V whereas other IP Phones use much less, i.e. 5-12V
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 -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 189 bytes Desc: Digital signature Url : http://lists.digium.com/pipermail/asterisk-users/attachments/20061121/9a09f6fa/attachment.pgp
Andrew Latham
2006-Nov-22 05:44 UTC
[asterisk-users] Why Aastra uses 48V whereas other IP Phones use much less, i.e. 5-12V
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@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@lathama.com - lathama@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. ---
Huib van Wees
2006-Nov-22 10:58 UTC
[asterisk-users] Why Aastra uses 48V whereas other IP Phones use much less, i.e. 5-12V
On 11/22/06, Zeeshan Zakaria <zishanov@gmail.com> wrote:> > Hi, > > 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? >48V is also a sort of "standard" for telco devices.... if I remember it correctly... -- Met vriendelijke groet / With kind regards, H. van Wees --- If UNIX isn't the solution, you've got the wrong problem. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20061122/94d80e00/attachment.htm
Steve Murphy
2006-Nov-22 14:14 UTC
[asterisk-users] Re: Why Aastra uses 48V whereas other IP Phones use much less, i.e. 5-12V
On Wed, 2006-11-22 at 12:01 -0700, asterisk-users-request@lists.digium.com wrote:> On 11/22/06, Zeeshan Zakaria <zishanov@gmail.com> wrote: > Hi, > > 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? > 48V is also a sort of "standard" for telco devices.... if I remember > it correctly... >IIRC, It's not just that 48 is a popular source. Most POE taps will regulate the voltage down to whatever they need, which often is just 5V, or 12V. But we are talking DC voltage here, and there are significant voltage drops due to the [small, but not zero] resistance of copper. The longer the cable from the injector to the tap, the bigger the resistance, and the more the voltage drop. The amount of current figures in there, also. So, 48V is a safer voltage in general to inject, as long lines will usually still see hopefully more than 5V at the tap end. If you are going to design networks with POE, you'd best pull out your calculator, multimeter, and V=IR equations, and see if you'll get the required voltage at the other end of the wire, given the current the devices will use. murf -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/x-pkcs7-signature Size: 3239 bytes Desc: not available Url : http://lists.digium.com/pipermail/asterisk-users/attachments/20061122/fbde0d4b/smime.bin
Michael Graves
2006-Nov-22 20:11 UTC
[asterisk-users] Why Aastra uses 48V whereas other IP Phones use much less, i.e. 5-12V
The amount of electricity used is constant. When run from 48v DC power they draw less current (mA)...power (w) is constant. Devices run from 5 V DC likely draw more current (mA). Power = Voltage x Current. Michael --Original Message Text--- From: Zeeshan Zakaria Date: Wed, 22 Nov 2006 21:29:46 -0500 Does it effect the performance/voice quality? Does this also mean that 48VDC is using less electricity in an office than 5VDC IP Phones? -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20061122/b860ce93/attachment.htm
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