TechMan is a fan of the "Dummies" series of books.

So as a service to readers (and we are a service column), TechMan is starting his own infrequent series called "TechMan's Quick and Dirty." Unfortunately, TQAD doesn't spell anything, like KISS (Keep It Simple, Stupid), but you can't have everything.

Today's TQAD topic is "How do cell phone companies differ technically, and should I care?"

The United States, with our attitude of "Let business do what it wants, no matter how bad for the consumer," has two standards for transmitting cell phone calls.

One is GSM (Global Systems for Mobile Communications, if you must know) and is the standard that Cingular and T-Mobile and most of the rest of the world use. CDMA (Code Division Multiple Access) is used by Verizon, Sprint, Virgin Mobile and parts of Asia.

So which one is better?

Coverage. There are areas in which only CDMA or GSM carriers offer coverage. There the choice is simple: Pick the one that works. But in most areas there is coverage by both.

CDMA has wider coverage in the United States, especially when you consider that only CDMA (especially Verizon) offers analog roaming so the phone can operate even if there is no digital service. GSM offers the best coverage worldwide.

Call quality. CDMA tends to do a better job handing off calls from one cell tower to another, and CDMA advocates claim the call clarity is better. But call clarity depends on so many factors that this claim is hard to prove.

Data transfer speed. With cell phones being used for everything from surfing the Internet to downloading movies, speed of data transfer becomes important. CDMA has traditionally been faster for data, and its EVDO high-speed service is comparable to basic DSL. It is not available everywhere.

GSM's data transfer format, EDGE, is not currently as fast, but new technologies are making it faster.

Choice. In the United States, only GSM phones can use removable SIM (Subscriber Identity Module) cards. SIM cards are tied to the carrier's network. With an SIM card you can keep the same phone and change the carrier or keep the same carrier and change the phone. You could use your U.S. GSM phone in Europe by plugging in a card.

There is no equivalent card for CDMA in the United States at this time.

To use a card, your phone must be unlocked, which U.S. GSM carriers are reluctant to do (because you could no longer be forced to buy the phone and service only from them).

However, the U.S. Copyright Office has ruled that consumers may legally break the software locks on their handsets in order to transfer service to another carrier. Still, you might have to be insistent to get a carrier to sell you an unlocked phone or a SIM card.

So which is better, GSM or CDMA? As usual with technology, the answer is "It depends."

For most people who just want a phone, go with the best-priced plan with the services you need that covers the area you inhabit.