What Is a Firewire® to USB Adapter

Firewire® (IEEE 1394) and USB (Universal Serial Bus) are two separate high-speed bus technologies that allow multiple devices to be connected to a computer. The two technologies are not integrated, and it is not possible to connect a USB device to a Firewire® port either directly. A Firewire® to USB adapter cable for transferring digital video (DV) is available from at least one manufacturer, but it can be expensive and difficult to find.

Even if you don't have a Firewire® to USB adapter cable, it doesn't mean that your Firewire® devices are useless if you have a USB port, or vice versa. Several companies do provide dual hubs. This type of device has two ports in a single hub, which may be either external or internal; one port is used Firewire® and one for USB, allowing either type of device to function. The combination hub is actually two separate ports combined into a single form factor for convenience; there is no conversion between Firewire® and USB taking place when you use one of these hubs.

Another alternative is simply to add two separate cards, assuming your computer has enough available slots. Firewire® and USB cards are both coming down in price, and adding whichever one is missing should not represent a major expense.

Both Firewire® and USB are efficient, high-speed bus standards. A Firewire® hub can support a data transfer rate of up to either 400Mbps or 800Mbps, depending on the standard, and a single Firewire® port can connect up to 63 devices and deliver a guaranteed rate of speed to each one. Firewire® is often used for devices that require real-time operation such as audio and video systems because of this guarantee, and it is also used frequently in storage area networks.

USB can connect more devices (up to 127), but supports data transfer rates of only up to 12Mbps. It is more often used for standard peripherals, such as mice, modems, and keyboards. The USB 2.0 standard supports speeds of up to 480Mbps, which makes it more competitive with Firewire®. On 17 November 2008, USB 3.0 specifications were released, with a transfer rate 10 times that of USB 2.0; consumer devices that use this standard were expected to be available by 2010.

If you cannot purchase a Firewire® to USB adapter, using a hub allows you to use devices that are compatible with either technology. Both technologies support Plug-and-Play and hot-plugging (hot-swappable).

What is the Difference Between GSM and CDMA

In cellular service there are two main competing network technologies: Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA). Cellular carriers including Sprint PCS, Cingular Wireless, Verizon and T-Mobile use one or the other. Understanding the difference between GSM and CDMA will allow you to choose a carrier that uses the preferable network technology for your needs. 

The GSM Association is an international organization founded in 1987, dedicated to providing, developing, and overseeing the worldwide wireless standard of GSM. CDMA, a proprietary standard designed by Qualcomm in the United States, has been the dominant network standard for North America and parts of Asia. However, GSM networks continue to make inroads in the United States, as CDMA networks make progress in other parts of the world. There are camps on both sides that firmly believe either GSM or CDMA architecture is superior to the other. That said, to the non-invested consumer who simply wants bottom line information to make a choice, the following considerations may be helpful.

Coverage: The most important factor is getting service in the areas you will be using your phone. Upon viewing competitors' coverage maps you may discover that only GSM or CDMA carriers offer cellular service in your area. If so, there is no decision to be made, but most people will find that they do have a choice.

Data Transfer Speed: With the advent of cellular phones doing double and triple duty as streaming video devices, podcast receivers and email devices, speed is important to those who use the phone for more than making calls. CDMA has been traditionally faster than GSM, though both technologies continue to rapidly leapfrog along this path. Both boast "3G" standards, or 3rd generation technologies.

EVDO, also known as CDMA2000, is CDMA's answer to the need for speed with a downstream rate of about 2 megabits per second, though some reports suggest real world speeds are closer to 300-700 kilobits per second (kbps). This is comparable to basic DSL. As of fall 2005, EVDO is in the process of being deployed. It is not available everywhere and requires a phone that is CDMA2000 ready. 

GSM's answer is EDGE (Enhanced Data Rates for GSM Evolution), which boasts data rates of up to 384 kbps with real world speeds reported closer to 70-140 kbps. With added technologies still in the works that include UMTS (Universal Mobile Telephone Standard) and HSDPA (High Speed Downlink Packet Access), speeds reportedly increase to about 275—380 kbps. This technology is also known as W-CDMA, but is incompatible with CDMA networks. An EDGE-ready phone is required. 

In the case of EVDO, theoretical high traffic can degrade speed and performance, while the EDGE network is more susceptible to interference. Both require being within close range of a cell to get the best speeds, while performance decreases with distance. 

Subscriber Identity Module (SIM) cards: In the United States only GSM phones use SIM cards. The removable SIM card allows phones to be instantly activated, interchanged, swapped out and upgraded, all without carrier intervention. The SIM itself is tied to the network, rather than the actual phone. Phones that are card-enabled can be used with any GSM carrier. 

The CDMA equivalent, a R-UIM card, is only available in parts of Asia but remains on the horizon for the U.S. market. CDMA carriers in the U.S. require proprietary handsets that are linked to one carrier only and are not card-enabled. To upgrade a CDMA phone, the carrier must deactivate the old phone then activate the new one. The old phone becomes useless.

Roaming: For the most part, both networks have fairly concentrated coverage in major cities and along major highways. GSM carriers, however, have roaming contracts with other GSM carriers, allowing wider coverage of more rural areas, generally speaking, often without roaming charges to the customer. CDMA networks may not cover rural areas as well as GSM carriers, and though they may contract with GSM cells for roaming in more rural areas, the charge to the customer will generally be significantly higher. 

International Roaming: If you need to make calls to other countries, a GSM carrier can offer international roaming, as GSM networks dominate the world market. If you travel to other countries you can even use your GSM cell phone abroad, providing it is a quad-band phone (850/900/1800/1900 MHz). By purchasing a SIM card with minutes and a local number in the country you are visiting, you can make calls against the card to save yourself international roaming charges from your carrier back home. CDMA phones that are not card-enabled do not have this capability, however there are several countries that use CDMA networks. Check with your CDMA provider for your specific requirements.

According CDG.org, CDMA networks support over 270 million subscribers worldwide, while GSM.org tallies up their score at over 1 billion. As CDMA phones become R-UIM enabled and roaming contracts between networks improve, integration of the standards might eventually make differences all but transparent to the consumer. 

The chief GSM carriers in the United States are Cingular Wireless, recently merged with AT&T Wireless, and T-Mobile USA. Major CDMA carriers are Sprint PCS, Verizon and Virgin Mobile. There are also several smaller cellular companies on both networks.

What Are Unlocked Cell Phones

Unlocked cell phones are mobile phones that can be used on any GSM network with interchangeable SIM cards. No matter which carrier makes the card, the phone will be able to recognize it and send voice and data over the network. This contrasts with a locked phone, which is bound to a specific cell phone service provider (or carrier) network with software settings, and is typically offered with a contract when someone starts mobile service.

Potential Advantages

One advantage to buying an unlocked cell phone is the ability to buy almost any GSM (Global System for Mobile Communications) phone, rather than being restricted to a limited selection offered by a specific carrier. This can include phones only distributed in certain countries, or with features that are not available on all carriers. People also don't need to wait for a contract to expire to buy a new phone; they can remove the SIM (Subscriber Identification Module) card from an existing phone and insert it into a new one when they are ready for a replacement. This allows them to keep their number while upgrading the phone, without having to go through the carrier.

Additionally, the ability to use an unlocked cell phone with a variety of SIM cards can be convenient for travelers. Most carriers only supply service to a particular country or area; when traveling outside the coverage zone, the mobile phone user will have to "roam" on another carrier's network, which often comes with a high fee. To avoid roaming fees, a person can buy a SIM card from a local carrier at his destination and insert it, preserving all his existing phone settings but getting a new number and a local calling plan. In addition to less expensive calling rates, this provides the added benefit of having a local number while in the area.

Potential Disadvantages

Not all unlocked phones have all the same features as their locked counterparts even when the provider is the same. Carriers may include such features only on locked phones, which use their proprietary software and settings. Some carriers offer free calling to a number of contacts or one-button access to certain features that can only be used on locked phones. Consumers concerned about specific features may want to check with a carrier to see if they are available on unlocked cell phones. 

In addition, such phones tend to be more expensive. Locked phones are often costly because they usually come with phone service contracts that commit the consumer to that service provider for a certain period of time (like two years). Unlocked phones typically sell at or close to retail price because the buyer can use the phone with a number of different carriers.

Another issue with unlocked cell phones is that they may not work on all GSM bands; as of 2012, a quadband phone could operate anywhere in the world with a GSM network, but other phones could not. This may be a concern for international travelers especially, since not all bands are used in all countries. For example, in South America, the 850 MHz band is in common use, but others may not be available. It is advisable to check on which bands the phone uses, and which bands are available in given travel destinations.

Getting an Unlocked Phone

One way to get a phone without proprietary settings is to buy it new from a third party vendor in its original, unlocked state. Third party services are also available to unlock a person's cell phone for a fee, usually by attaching it to a special piece of hardware specially designed for this purpose. This doesn't guarantee the phone will always work correctly, as carrier settings might remain in the software. 

There are also instructions online to unlock most models. In many cases, unlocking a phone is just a matter of activating the phone and entering a specific code; some phones, however, require a series of steps before the code can be entered. Not all codes work, and trying to enter codes that are incorrect can cause the phone to "hardlock" and prevent it from being unlocked. Certain models of cell phones can only be unlocked using the hardware method, which may also worked for hardlocked phones.

Some cell carriers sell unlocked phones at full price, usually allowing consumers to pick a flexible plan such as month-to-month or pay-as-you-go billing. This can provide access to carrier-specific features with the flexibility of an unlocked phone. If a customer has been with a carrier for some time — sometimes for as little as 90 days — the carrier may even be willing to supply an unlock code for a locked phone, although they may charge a fee.

Cell Phone Carriers

The majority of the world — 99% — uses the GSM network, and numerous carriers use it for their services. The competing network is CDMA, or code division multiple access. Most carriers on the CDMA network do not, as of 2012, use card-enabled phones; instead, subscriber information is stored in the cell phone's memory, which means it cannot be transferred to another phone. The CDMA equivalent of the SIM card — the R-UIM — is likely to be used by these carriers in the future, and is already in use in some parts of Asia. This card contains software that allows it to be used in GSM phones as well.

Jailbroken Phones

A jailbroken phone is not exactly the same as an unlocked phone. Most often used in reference to Apple's iPhone®, when a phone is jailbroken, it has been modified to allow it to download applications (apps) not approved or sold by the carrier, such as the Apple App Store. A phone that has been jailbroken is not unlocked, although it may be necessary to jailbreak a phone before unlocking it is possible. Jailbreaking a phone is considered legal in the US, although it may violate the warranty.