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Main > Electronics > Telecommunications

How Cell Phones Work
by Marshall Brain and Jeff Tyson


 Introduction to How Cell Phones Work
The Cell Approach
From Cell to Cell
Cell Phones and CBs
Inside a Cell Phone
AMPS
Along Comes Digital
Cellular Access Technologies
Cellular vs. PCS
› Dual Band vs. Dual Mode
Problems with Cell Phones
Cell-phone Towers
Lots More Information

Dual Band vs. Dual Mode
If you travel a lot, you will probably want to look for phones that offer dual band, dual mode or both. Let's take a look at each of these options:
  • Dual band - A phone that has dual-band capability can switch frequencies. This means that it can operate in both the 800-MHz and 1900-MHz bands. For example, a dual-band TDMA phone could use TDMA services in either an 800-MHz or a 1900-MHz system.
  • Dual mode - In cell phones, "mode" refers to the type of transmission technology used. So, a phone that supported AMPS and TDMA could switch back and forth as needed. It's important that one of the modes is AMPS -- this gives you analog service if you are in an area that doesn't have digital support.
  • Dual band/Dual mode - The best of both worlds allows you to switch between frequency bands and transmission modes as needed.
Changing bands or modes is done automatically by phones that support these options. Usually the phone will have a default option set, such as 1900-MHz TDMA, and will try to connect at that frequency with that technology first. If it supports dual bands, it will switch to 800 MHz if it cannot connect at 1900 MHz. And if the phone supports more than one mode, it will try the digital mode(s) first, then switch to analog.

Sometimes you can even find tri-mode phones. This term can be deceptive. It may mean that the phone supports two digital technologies, such as CDMA and TDMA, as well as analog. But it can also mean that it supports one digital technology in two bands and also offers analog support. A popular version of the tri-mode type of phone for people who do a lot of international traveling has GSM service in the 900-MHz band for Europe and Asia and the 1900-MHz band for the United States, in addition to the analog service.

In the next section, we'll touch on some of the problems encountered with cellular phones.

Lowest Price
1.Sprint Samsung SPH-i500 Mobile Phone $549.99
2.Handspring TREO 600 GSM/GPRS COMMUNICATOR CELLPHONE PALM ORGANIZER WIRELESS $499.00
3.Handspring Treo 270 Communicator - Phone & PDA - No Service $99.00
4.Sony Ericsson P900 (unlocked) $500.00
5.TREO 600 PDA/PHONE SPRINT PCS NETWORK ONLY WIRELESS CDMA $599.95

 

 
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Table of Contents:
Introduction to How Cell Phones Work
The Cell Approach
From Cell to Cell
Cell Phones and CBs
Inside a Cell Phone
AMPS
Along Comes Digital
Cellular Access Technologies
Cellular vs. PCS
› Dual Band vs. Dual Mode
Problems with Cell Phones
Cell-phone Towers
Lots More Information


 
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