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Cell Phone Secrets
Posted on: 2007-04-03 17:00:27
I am a mobile telecommunications "engineer", and I thought I'd explain what to look for in a cell phone. Most guides will review phones on their user interface, but pay little attention to one of the most important pieces: the radio. The radio on GSM cell phones is very mysterious to most people, so here is a guide on how to decode the features of cell phones.


The bands your mobile phone supports will depend on the region in which you live. In the year 2006, four bands are in common use: 850, 1900, 900, and 1800 MHz. The 850/1900 bands are used in North America, while the rest of the world (with a few exceptions) uses the 900/1800 bands. Your carrier will likely deploy either 850/1900 or 900/1800 in your area, so for maximum coverage your phone should support the two bands in use in your region.

If you are traveling, you will want a Tri-Band or Quad-Band phone. A Tri-Band phone supports the two bands in your country, plus one other one. It may also be advertised as a "World Band" phone. A Quad-Band phone will support all four bands.

All phones sold today should automatically detect and switch between the bands.


GPRS refers to the ability of the phone to transfer packet data (for example, emails, ring tones, and web pages). The speed of the connection is related to the multislot class. EDGE is an enhancement to GPRS that allows faster data rates, comparable to broadband connections. If all you want is phone calls, you should ask your carrier to disable your packet access, to avoid incurring usage charges by accident.


UMTS handsets, also called "3G", support a new technology that will theoretically give you faster data access than EDGE. However, because they are a newer technology, their battery life will be much less than a GSM-only phone. In addition, UMTS base stations are deployed only in major metropolitan centres. Recently, in the Blackjack phone, users discovered if they turned off the 3G feature, their battery life doubled!

If you are only making phone calls, you don't need this. It helps the carriers because it moves phone calls off of their congested GSM cells, onto their UMTS cells that hardly anybody uses at the moment. If you do want a data modem, you should consider it, because the higher data speeds will be noticeable.

Multislot class

The multislot class of your phone determines how quickly it will transmit or receive packet data. (For example, emails and web pages, but not voice or SMS messages.) Most phones will be Multislot Class 10, which means it can receive on four different channels simultaneously, or send on two different channels. Higher multislot classes allow more channels, and thus it will be faster. However, if the cell tower is being used by more than a few mobiles at the same time, this won't make any difference, because it will run out of channels.

Multislot class only applies to packet data, like web pages or picture messages. Phone calls only use one slot, anyway.

Dual Mode

A dual-mode handset will support two different radio technologies and switch between them when appropriate. For example, because UMTS base stations are deployed only in major cities, a UMTS handheld will probably be able to fall back on GPRS technology when you roam away from the city.

Dual transfer mode

Dual transfer mode handsets are expected to be deployed to some networks in 2007. With dual transfer mode, you will be able to transfer packet data during a phone call. This is something already supported by UMTS but not GSM, so there is a greater push for it in GSM phones.


Audio engineers love flip phones, because it brings the microphone closer to the mouth. Companies spend millions of dollars, and hire lots of Ph.D's to try to get the microphone to work when it is on your cheek, but a handset designer will tell you that you can get the best audio quality with a flip phone.

Data Modem

If your phone has data modem capabilities, you will be able to attach it to your computer and use it as a modem. However, be aware that your transfer speeds will be limited. GPRS/EDGE phones have an inherent limitation: The very first packet that you send (after a break of about 5 seconds) will take up to 1.5 seconds to start the transfer, although subsequent packets will be faster. This makes GPRS modems inefficient for the TCP protocol used by all networked PCs today. However, you should still be able to browse at speeds similar to dial-up.

Make sure to read the fine print: Your "unlimited" plan may actually only include a few MB/month, with steep charges if you go over the limit. The limit is especially troubling, because Microsoft Windows will typically send several megabytes of data in a few minutes, because a lot of the software that you have will constantly be checking for updates.

Talk and Standby Time

Talk time and standby time are tested in a standardized way. Because they are not real conditions, handset manufacturers can employ certain tricks to get a better rating. Look for a talk time of at least 4 hours, and a standby time of at least 10 days, whether you need it or not.

All rechargeable batteries have a limited life. They are killed by both heat and time. You should get a lithium battery, which will last for several years. Nickle-Metal-Hydride (NiMH) batteries are good too, but exhibit a "memory-effect", which means that you should charge them only when they are close to empty. NEVER leave a battery the car in hot weather, because this shaves months off of its life. When you are replacing it, buy only a newly manufactured battery, because they will slowly die even if left in the package. For this reason, don't bother getting a spare when you buy the phone. If you do want to store your battery for a period of time, discharge it to 40%, and keep it in the refrigerator inside a sealed plastic bag. Make sure it is dry, or the contacts will rust.

The more gadgets your phone has, the more the battery will run out. External memory slots, GPS, and Wi-Fi are all things that will suck the juice out of your battery. Also, if you live on the fringes of coverage and get only 1 to 3 bars of service, your battery will only last a couple of days because the phone will have to transmit at maximum power. GSM phones have to update with the network every 5-15 minutes, so they will consume power even if you are not using it.


The industry is working on a new feature, called GAN or UMA, which is already available in some areas. In an UMA phone, the carrier will also sell you Internet access and give you a wireless access point. While in your home, your calls will go through the Wi-Fi connection. When you leave your house, the calls will be handed over to the cellular (even if you are talking). This means that you will always get full service in your home, but it will also reduce the standby time. You should get it only if you want to buy Internet service from your carrier.

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2007-08-13 19:04:09
Can the ip addresses of two mobile phones be the same? Please reply to my email silkworm@webmail.co.za

Steve Hanov

2007-09-25 22:50:52

Mobile phones do have IP addresses, but they are not useful to you. If you try to ping one, for example, it won't work because there is a lot of carrier infrastructure between the public internet and the phone.

When your mobile phone connects to the network, it is assigned an IP address inside the carrier's network. Any data that it sends is forwarded through the carrier's servers, and the carrier will perform network address translation (NAT). That means that you will only be able to make outgoing connections.

The network is tightly controlled, so I doubt that one phone will be able to directly access another, even if they are on the same carrier's network.

Edwin Sligar

2008-07-15 15:29:30
I know that GSM is full duplex, but does the phone actually transmit and receive at the same time?


2009-03-20 22:52:16
i am having a cell phone name sagem and the model is my300c and i want to decode it ok.i want u to show my the code to open it ok thanx

Steve Hanov

2009-05-02 10:10:06
GSM appears to send and receive at the same time, because you can talk and listen to a phone call. But the radio transmitter cannot receive and transmit at the same instant. The phone continously switches between receiving and transmitting every 4.62 milliseconds.


2009-06-27 09:05:21
hey i have a problem i have a girlfriend who talks to me on messenger off a mobile and she keeps sighning out and sighning bk in strait away still on a mobile and when she sighns bk in its like shes a completely different person i have a little suspision its sum one else im talking to and i was just wondering is there any way mobile phones have diff signitures and how i can c if its her mobile she sighns bak in on or a different one your help would be gratfefull thanks plz reply to maty0255@hotmail.com


2009-07-07 12:27:58
please my beautiful girl that am about to be married to seems to have someone that pesters her(according to her). how can i be sure she aint returning his advances. is they a way to listen to her calls without her knowledg. pls reply thru jjpenkiss@yahoo.com or usibesvision@gmail.com


RJ Rhymer

2009-07-15 12:14:16
How do you decode a cell phone, so that it will work with any carrier.


2011-12-03 05:46:57
What is with all this weird comments

Jennifer farris

2013-07-26 21:47:23
Hi Steve I was wondering if someone is sending me annoymous emails from a bogus acct they created over a cell phone network am sent the email over the cell phone network can this be traced?

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