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When families pack for a long trip overseas, they confront the issue of staying in touch with those back home.

Traveling families preparing for an international getaway will grapple with two practical issues they'd rather leave behind — money (whether to carry and use traveler's checks, credit cards, cash or an ATM) and how to stay in touch. The latter challenge is examined here.

There are several options for telecommunications in a foreign country. If you don't need (or want) an easy way for people at home to reach you, and don't mind not having a cellular phone, buy a local phone card. If you want to carry a cell phone with you, for whatever reason, your options will depend on a number of factors, especially the volume of calls you expect to make. The decision is complicated by the various technologies, so stick with me and we'll work through the learning curve together.

GSM & CDMA Standards

Let's define the key vocabulary straight away. Throughout the world, there are several different wireless operating standards—GSM, CDMA, TDMA, IDEN, AMPS. Only the first two will affect most cell phone customers in the U.S.

The GSM standard is used in more countries (currently numbering 205) than the CDMA standard. Within the GSM standard, there are four operating frequencies, comparable to FM station frequencies. The most common GSM phones are dual-band and will have frequencies working internationally (900MHz and 1800 MHz) and in the U.S. (850 MHz and 1900 MHz).

Make sure that your phone has the required bands for international travel. T-Mobile and ATT/Cingular operate under the GSM standard and will work in most GSM countries.Verizon and Sprint are now offering a few phones with GSM capabilities, under the "global phone" banner (However, they are currently somewhat expensive, as are their roaming rates).Only Japan and South Korea are strictly CDMA and a T-Mobile or ATT/ Cingular phone will not work there). If you are buying for international travel, you should purchase either a tri-band 900/1800/1900 or quad-band 850/900/1800/1900.

Other U.S. wireless operators (Verizon, Sprint) primarily use the CDMA standard, which is in use in a few other countries and on most cruise ships. In these CDMA situations, your own CDMA phone will probably work, though at roaming rates which can be costly ($.69-2.49).. These CDMA compliant countries include USA, Canada, Mexico, China, Israel, New Zealand, Thailand, and many Caribbean countries. Check with your wireless provider for a full list. (These countries also have GSM networks) A CDMA phone will not work in a GSM country.

SIM Cards

All GSM phones (but not CDMA models) have a removable SIM (Standard Information Module or Subscriber Identity Module) card inside, which is about the size of a postage stamp and usually found under the battery. These SIM cards interact with the wireless systems available to the phone. There are several kinds of SIM cards which can work with your GSM phone, but the U.S. wireless carriers sell their phone in a 'locked" mode, which restricts usage to their proprietary SIM cards and service. There is a solution, however.

Both T-Mobile and ATT/Cingular (but not yet Verizon and Sprint) will provide unlock codes on request, freeing you to use any SIM card. There are several varieties available that provide cheaper service than available with the original proprietary card--country-specific cards for service in individual countries or "roaming" (a.k.a "global") cards that work in multiple countries. Both kinds of cards offer free incoming calls and text messages in most countries, a significant savings over the carrier proprietary cards.

With the country cards, your phone is a "local" phone, with a phone number of that country. With a roaming card, you dial the destination number, then receive a call back, which, when answered, connects ,to the number. It's a slightly odd system, but it works. Your cell phone number will be based in a European country (U.K., Estonia, etc.). The cost saving is well worth any hassle. Note that a pre-paid SIM card can cost around $60, but may only have $10 worth of airtime. You will need to recharge the card as it runs low, either with pre-paid recharges, by buying the recharge locally in your country, or with roaming cards, by credit card.