Re: [asterisk-users] Why Aastra uses 48V whereas other IP Phones use much less, i.e. 5-12V
On Wed, 22 Nov 2006 19:20:54 +, Steve Kennedy wrote: On Wed, Nov 22, 2006 at 06:58:13PM +0100, Huib van Wees wrote: On 11/22/06, Zeeshan Zakaria [EMAIL PROTECTED] wrote: 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... Power is nothing to do with voltage (well it is, but not alone), you need the current too i.e. V * A. Pylon electricity lines run at very high voltage (several hundred thousand volts) or the current going down the lines would heat the cables and you'd lose a lot of power. 48V is just a telco standard, and most telco equipment (that runs in racks) is 48V. Probably because 110 (or 220/240 here in EU) is enough to electrocute an engineer, and 5V/12V would require too many Amps so wiring would have to be huge to carry the current. Yes, 48v dc is a telco standard. It has to do with how they build their facilities and efficiencies in electrcal use. When your entire plant has to be on a UPS you can save much money and gain reliability by NOT having AC power supplies in every bit of gear. Thus they have standard 48v DC UPS infrastructure and everything plugs into it. This is the way to 99.999% uptime from a power perspective. It's interesting to note that outfits such as Google are now going down a similar route in planning huge new datacenters. Michael Graves ___ --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
Re: [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 [EMAIL PROTECTED] 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) [EMAIL PROTECTED] - [EMAIL PROTECTED] If any of the above are down we have bigger problems than my email! Hind sight is most always 20/20 or better. --- ___ --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
Re: [asterisk-users] Why Aastra uses 48V whereas other IP Phones use much less, i.e. 5-12V
On Wed, Nov 22, 2006 at 06:58:13PM +0100, Huib van Wees wrote: On 11/22/06, Zeeshan Zakaria [EMAIL PROTECTED] wrote: 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... Power is nothing to do with voltage (well it is, but not alone), you need the current too i.e. V * A. Pylon electricity lines run at very high voltage (several hundred thousand volts) or the current going down the lines would heat the cables and you'd lose a lot of power. 48V is just a telco standard, and most telco equipment (that runs in racks) is 48V. Probably because 110 (or 220/240 here in EU) is enough to electrocute an engineer, and 5V/12V would require too many Amps so wiring would have to be huge to carry the current. Steve -- NetTek Ltd UK mob +44-(0)7775 755503 UK +44-(0)20 79932612 / US +1-(310)8577715 / Fax +44-(0)20 7483 2455 Skype/GoogleTalk/AIM/Gizmo/Mac stevekennedyuk / MSN [EMAIL PROTECTED] Euro Tech News Blog http://eurotechnews.blogspot.com ___ --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
Re: [asterisk-users] Why Aastra uses 48V whereas other IP Phones use much less, i.e. 5-12V
Power is nothing to do with voltage (well it is, but not alone), you need the current too i.e. V * A. Pylon electricity lines run at very high voltage (several hundred thousand volts) or the current going down the lines would heat the cables and you'd lose a lot of power. 48V is just a telco standard, and most telco equipment (that runs in racks) is 48V. Probably because 110 (or 220/240 here in EU) is enough to electrocute an engineer, and 5V/12V would require too many Amps so wiring would have to be huge to carry the current. The 48V standard came from what was the station battery. This dates back to very early telephone standards (think operators at desks with patch chords). The station battery is hooked up to power the equipment with the positive terminal at ground. On hook voltages (between tip and ring) were derived from this battery. Once a phone goes off hook with 600 Ohms of resistance the voltage across tip and ring drops to roughly 6 V. The power coming over the line is expected to be sufficient to power the phone. Station batteries were intended to be stable permanent power sources much an UPS except without the conversion back to AC. As a matter of further information regarding voltages: Ring voltage is double the 48 volts alternating at 20Hz. I believe that the number of amps that can be driven determines the maximum ringer equivalence rating for a circuit. Ringer equivalence is a non issue for most modern phones. Especially phones with external power sources. This is reproduced from memory. If I recalled incorrectly corrections are welcome. Shaun -- Visit my blog at http://hackerlog.blogspot.com = If more of us valued food and cheer and song above hoarded gold, it would be a merrier world. -- J.R.R. Tolkien ___ --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
Re: [asterisk-users] Why Aastra uses 48V whereas other IP Phones use much less, i.e. 5-12V
Does it effect the performance/voice quality? Does this also mean that 48VDC is using less electricity in an office than 5VDC IP Phones? ___ --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
Re: [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? ___ --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
[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 ___ --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
Re: [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 signature.asc Description: Digital 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
