Knowledge base about unlocked GSM cell phones:

What You Should Know

What Is GSM?
GSM (Global System for Mobile Communications) has become the most successful global mobile technology for mobile phones and digital cellular networks with more than one billion subscribers.
GSM phones require a small electronic chip, which is called a SIM card, to be inserted into a slot in the handset. This international SIM card is the important part of your phone - it contains your cell phone number, your phone book, and all of your registration information. Most companies with GSM service provide you access to over 320 GSM networks in over 140 countries.

What does Unlocked GSM Phone mean?
Unlocked GSM phones are either phones which are directly from the manufacturer which were never locked, or phones from a carrier which have been modified to openly work on any network. With Unlocked Cell Phones you could use your own SIM card.

What are the frequencies of GSM?
Most of the world's GSM networks operate at 900MHz and 1800MHz. However, in order to use the networks in the USA and Canada you will need a handset that is also capable of operating at the 1900MHz frequency. Most phones are now either "dual" "tri" or "quad band" (includes 850MHz) to serve most of the world. Call your carriers to find out what frequencies you have.

What Is GPRS and What is the Benefits?
GPRS (General Packet Radio Service) is the world's most ubiquitous wireless data service, available now with almost every GSM network. GPRS is a connectivity solution based on Internet Protocols that supports a wide range of enterprise and consumer applications. With throughput rates of up to 40 kbit/s, users have a similar access speed to a dial-up modem, but with the convenience of being able to connect from anywhere. GPRS customers enjoy advanced, feature-rich data services such as color Internet browsing, e-mail on the move, powerful visual communications such as video streaming, multimedia messages and location-based services.
For operators, the adoption of GPRS is a fast and cost-effective strategy that not only supports the real first wave of mobile Internet services, but also represents a big step towards 3GSM (or wideband-CDMA) networks and services.

What is Bluetooth wireless technology and How does it work?
Bluetooth is a specification for the use of low-power radio communications to wirelessly link phones, computers and other network devices over short distances. The name "Bluetooth" is borrowed from Harald Bluetooth, who was a king in Denmark more than 1,000 years ago.

Bluetooth technology was designed primarily to support simple wireless networking of personal consumer devices and peripherals, including cell phones, PDAs, and wireless headsets. The wireless signals transmitted in Bluetooth reach over short distances, typically up to 30 feet (10 meters). Bluetooth devices generally communicate at less than 1 Mbps.

Bluetooth networks feature a dynamic topology called a piconet or PAN. Piconets contain a minimum of two and a maximum of eight Bluetooth peer devices. Devices communicate using protocols that are part of the Bluetooth Specification.

Although the Bluetooth standard utilizes the same 2.4 GHz range as 802.11b and 802.11g, Bluetooth technology is not a suitable Wi-Fi replacement. Compared to Wi-Fi, Bluetooth networking is much slower, a bit more limited in range, and supports many fewer devices.

As is true for Wi-Fi and other wireless technologies today, concerns with Bluetooth include security and interoperability with other networking standards.

What is Java?
Java is a software technology developed to provide a common base for running applications across a wide variety of computing platforms. It consists of a programming language and a run-time environment.

Java applications can run on servers, personal computers, mobile phones and other devices. Because the capabilities of these computing platforms vary, Java has evolved into 3 editions:

1.) Java 2 Enterprise Edition (J2EE) - for high-end business machines
2.) Java 2 Standard Edition (J2SE) - for personal computers
3.) Java 2 Micro Edition (J2ME) - for smaller handheld devices such as mobile phones and PDAs

The Mobile Information Device Profile (MIDP) is a key element of the J2ME, defining a platform for dynamic networked applications. Developers using MIDP can write applications once, then deploy them to a wide variety of mobile devices. MIDP has been widely adopted as the platform of choice for mobile applications.

How does it work?
Software written in Java is independent of operating systems, as the instructions are interpreted in the computer at the time when the software is run, not beforehand. Every computer or device that runs a Java application must have a Java Virtual Machine that adapts the application code for the specific device and before executing it.

What is 3G?
3G is an ITU specification for the third generation (analog cellular was the first generation, digital PCS the second) of mobile communications technology. 3G promises increased bandwidth, up to 384 Kbps when a device is stationary or moving at pedestrian speed, 128 Kbps in a car, and 2 Mbps in fixed applications. 3G will work over wireless air interfaces such as GSM, TDMA, and CDMA. The new EDGE air interface has been developed specifically to meet the bandwidth needs of 3G.