Telephone Power
2010
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 Cisco ATA 186 Analog Telephone Adaptor +power adapter $79.99 Time Remaining: 12d 19h 38m Buy It Now for only: $79.99 |
 Arris TM502G Telephone Modem Power SupplyCat5 Cable $40.00 Time Remaining: 16h 37m Buy It Now for only: $45.00 |
 Aastra Packet 8 6755i 55i IP Telephone IP Phone with Power Adapter $94.99 Time Remaining: 10d 1h 5m Buy It Now for only: $94.99 |
 Grandstream HandyTone 702 HT702 ATA Analog Telephone Adapter 2 FXO 1 LAN w Power $45.00 Time Remaining: 2d 16h 19m Buy It Now for only: $45.00 |
 Televantage ST2118 LCD VOIP Virtual Office Telephone with Power Supply $19.99 Time Remaining: 17h 12m Buy It Now for only: $19.99 |
 Vonage Motorola VT2142 VC VOIP Telephone Adapter NO POWER ADAPTER $12.72 Time Remaining: 6d 6h 10m Buy It Now for only: $12.72 |
 Phone Power Broadband Telephone Service Combo Pack $43.97 Time Remaining: 25d 13h 37m Buy It Now for only: $43.97 |
 AltiGen Alti IP705 Alti IP 705 with Power Supply 3G Voip Phone Telephone $125.00 Time Remaining: 23d 14h 15m Buy It Now for only: $125.00 |
 New Polycom Soundpoint IP 331 VoIP SIP Phone Telephone w Power Supply $20.50 (6 Bids) Time Remaining: 22h 17m |
 Cisco SPA942 VoIP 4 line IP Phone LINKSYS VOIP IP Telephone w Power Supply $80.00 Time Remaining: 21d 21h 1m Buy It Now for only: $80.00 |
 2 Used Mitel 5220 IP dark grey telephone with power supply and Cat5 phone $49.00 Time Remaining: 19d 19h 46m Buy It Now for only: $49.00 |
 Nortel NTDU76 i2002 IP Telephone with dektop stand and power adapter $29.99 Time Remaining: 1d 20h 1m Buy It Now for only: $29.99 |
 1 Used Mitel 5220 IP dark grey telephone with power supply Cat5 phone head rest $28.00 Time Remaining: 19d 19h 43m Buy It Now for only: $28.00 |
 Westell Versa Link Model 327W DSL Modem w Ethernet Telephone Power Cable Antenna $20.00 Time Remaining: 7d 19h 44m Buy It Now for only: $20.00 |
 1 Used Mitel 5220 IP dark grey telephone with power supply and Cat5 phone $28.00 Time Remaining: 19d 19h 41m Buy It Now for only: $28.00 |
 Lot of 2 Cisco 7941 Series IP Office Telephones CP 7941G Powered On Untested $75.00 Time Remaining: 5d 15h 45m Buy It Now for only: $100.00 |
 Lot of 5 IP Telephone POWER ADAPTERS GS 768 GT 21089 1948 T3 $34.60 Time Remaining: 4d 17h 7m Buy It Now for only: $34.60 |
 CISCO Linksys SPA921 1 Line VoIP SIP IP Telephone 1 LAN Port with Power Adapter $119.00 Time Remaining: 22d 19h 1m Buy It Now for only: $119.00 |
 1 Used Mitel 5220 IP dark grey telephone with PKM 5412 power supplycat5 phone $34.00 Time Remaining: 19d 19h 43m Buy It Now for only: $34.00 |
 NEC AC 3R UNIT Power Adapter Part 780152 NEW $35.90 Time Remaining: 8d 20h 48m Buy It Now for only: $35.90 |
 Avaya IP Power Supply 1151C1 NEW IN BOX $32.95 Time Remaining: 24d 20h 29m Buy It Now for only: $32.95 |
 Syspine Syspine A50Plus 310 IP Speakerphone Power Over Ethernet SYS A50P 310M $91.84 Time Remaining: 1d 16h 6m Buy It Now for only: $91.84 |
 Avaya 9630G IP Telephone W Power Supply $149.99 Time Remaining: 6d 18h 18m |
 Avaya IP Power Supply 1151C1 BRAND NEW IN BOX $29.00 Time Remaining: 18d 22h 55m Buy It Now for only: $29.00 |
 Cisco ATA186 I1 A Analog Telephone Adapter Power Cube included Quantity 15 $175.00 Time Remaining: 9d 12h 17m Buy It Now for only: $175.00 |
 Packet8 ST 2118 VOIP telephone + BPA410 Broadband Adaptor + power supplies $19.99 Time Remaining: 13h 28m Buy It Now for only: $19.99 |
 Eutectics IPP2000 Internet Power Phone Standard Telephone Adapter $45.00 Time Remaining: 14d 18h 11m Buy It Now for only: $45.00 |
 Phone Power Broadband Telephone Service Combo Pack $79.95 Time Remaining: 1h 34m Buy It Now for only: $79.95 |
 Nortel Networks i2002 IP Telephone w Power Supply NTDU76AB34 $59.99 Time Remaining: 20d 16h 33m Buy It Now for only: $59.99 |
 Avaya 1151C2 Power Supply Power Over Ethernet IP Telephone DCP Telephone $9.99 Time Remaining: 6d 22h 34m |
 PACKET8 ST2118 VOIP TELEPHONE RJ11 POWER ADAPTER $65.00 Time Remaining: 22d 17h 23m Buy It Now for only: $65.00 |
 NEW PA100 Power Supply For Cisco IP Telephone $14.99 Time Remaining: 9d 16h 42m Buy It Now for only: $14.99 |
 Cisco ATA 186 188 Analog Telephone Adapter with ac 5v Power Adapter NOT WORKING $89.10 Time Remaining: 25d 15h 15m Buy It Now for only: $89.10 |
 CISCO ATA186 I1 A W POWER CORD ANALOG TELEPHONE ADAPTER ATA 186 $150.00 Time Remaining: 10d 18h 15m Buy It Now for only: $150.00 |
 ACTIONTEC ED800T Ethernet USB Home DSL MODEM power adapter cord telephone cord $7.99 Time Remaining: 28d 4h 24m Buy It Now for only: $7.99 |
Telephone Power
All About Cordless Telephone
A cordless telephone (telefone sem fio) is an electronic telephone that comprises of a wireless handset and a base unit. Communication is carried out between the handset and the base using radio waves. The wireless handset can be operated only within a fixed range from its base unit. The range of operation is generally within 100 meters. The base unit needs electricity to power it. Batteries are used to power the cordless handset. Placing the cordless handset in the cradle in the base unit recharges these batteries. A period of 12 to 24 hours is required for recharging the batteries.
With features like cell handover, data transfer and international roaming (on a limited scale), the once clear-cut line between mobile telephones and cordless telephones (telefone sem fio) has now been blended by the modern cordless telephone standards.
Frequency bands have been assigned in each country for cordless telephones (telefone sem fio). Advertisements by manufacturers claiming that there is an improvement in audio range and quality with higher frequency are a common sight. But that is not the case. Actually, higher frequencies have been seen to exhibit worse propagation in ideal case. There is also a tendency for the path loss to increase with higher frequencies. Locally varying factors such as antenna quality, signal strength, the modulation method being used and interference are more influential than other factors.
With Landline telephones working on a bandwidth of about 3.6 kHz (a small fraction of the frequency that a human ear can interpret), the transfer of audio is carried out with an audio quality that is just enough for the parties to communicate each other. Because of this limitation in the design of the phone system itself, it is not possible to improve the audio quality beyond a particular limit in cordless telephones.
Most of the good-quality cordless telephones (telefone sem fio) try transferring the audio signal with lowest possible interference and greatest possible range. Even the best of the cordless telephones fail to match the audio quality that a high quality phone wired to a good telephone line provides.
Sidetone (echo of voice heard in the speaker of the receiver), disturbing constant background noise that is due to the cordless system, and inability to obtain a full frequency response that is available in a wired phone are few of the reasons for a not-so-good audio quality. Rare exceptions, obviously, always exist that sound unbelievably similar to a wired telephone. But even these are considered as `fluke` by most industry standards.
Higher frequency is now being used in other home products like the microwave oven, Baby monitor, Bluetooth, wireless LAN, etc. Thus, cordless telephones (telefone sem fio) using higher frequency may face interference from signals from these devices.
Eavesdropping is a constant security threat for analog telephones. Any one with a radio scanner and within range can pick up these signals and listen to conversations. Modern digital technology is thus being used to take care of this kind of unauthorized access.
DSS (Digital Spread Spectrum) makes use of frequency hopping, i.e. spreading up of audio signal over a wider range in a pseudorandom fashion. DSS signal sounds like noise bursts to a radio scanner or any other analog receiver. This signal makes sense only to that base unit which has the same pseudorandom number generator as the cordless handset. Each time the cordless handset is returned to its cradle, a new unique generator is chosen from thousands of options.
DSS generates a signal spread that leads to a kind of redundancy, which gives rise to increased signal-to-noise ratio. It also leads to increase in signal range and decreases interference susceptibility. It is easier to use this kind of wide-bandwidth security option with higher frequency.
This article is under GNU FDL license and can be distributed without any previous authorization from the author. However the author's name and all the URLs (links) mentioned in the article and biography must be kept.
About the Author
This article can also be accessed in portuguese language from the Article section of page www.polomercantil.com.br/telefone-sem-fio.php
Roberto Sedycias works as IT consultant for www.PoloMercantil.com.br
Telephone Line as a Power Source?
I've read that the conventional telephone line outputs about 48 volts when off the hook (not in use). I'm wondering if it's possible then to use it as an emergency power supply in case of power failure. Also, how much power does it normally output?
it is 48VDC when ON hook... NOT OFF hook... off hook is when the phone is in use, and off hook is ~9VDC
there is very little amperage going thru a phone line, so you would not be able to draw much current from the phone line, plus ringing voltage is 90VAC - which would likely fry whatever low voltage DC powered devices that you were trying to power...
but if you still feel the need to get power from the phone company sandman has some stuff on his site that is telephone company line powered... not sure if this is more just a novelty though...
http://www.sandman.com/telco.html
EDIT - after reading the bottom of that page i am almost certain that it is fake...
Telephone RJ11 Power Saved 8 LED Table Desk Reading Lamp
