Istanbul, Turkey — I’m in a city that spans Asia and Europe yet I’m happily using cell phones from Sprint and Verizon Wireless.

I’ve always thought of Sprint and Verizon as purely domestic carriers, serving only the U.S. market, but that’s not the case. Even though most phones from these two popular U.S. carriers are configured to access cellular networks that are totally incompatible with the GSM (Global System for Mobil) networks used in Europe, Australia, parts of Asia, Africa and much of the rest of world, both companies do offer phones that are also capable of accessing GSM networks overseas.

For example, both Verizon and Sprint sell the BlackBerry 8830 World Edition (prices vary by carrier and service plan) while Sprint also has a Samsung Ace Windows Mobile SmartPhone and Verizon the Motorola Z6c World Edition. Each of these phones uses its carrier’s CDMA network in North America but is also equipped with GSM SIM cards for use in other countries. Also, most of Verizon’s phones, according to the company’s Web site, do work in Israel, Brazil, Thailand, South Korea and a few other countries, but not in most of the world. AT&T and T-Mobile use GSM technology that does work in most countries.

SIM stands for “Subscriber Identity Module.” All GSM phones have a slot for this tiny card that is required for them to make and receive calls.

From my present vantage point in Turkey and after stops in Majorca, Spain and London earlier this week, I can testify that the Verizon and Sprint phones work great in the places I’ve visited. Sprint loaned me the Samsung Ace and Verizon provided me with a BlackBerry 8830 for testing, and with both phones I’ve been able to make local calls as well as international calls to the United States and other countries. Data service also works with full access to e-mail, text messaging and Web browsing. And, perhaps because of Europe and Turkey’s extensive GSM network, the sound quality and coverage is as good as or in many cases better than in the United States, even from when I used the phone from a relatively rural areas of Spain and England.

Both Sprint’s and Verizon’s world BlackBerrys can use the high-speed 3G network in much of the world. Sprint’s Ace uses Sprint’s high-speed EVDO network in the United States but reverts to somewhat slower networks overseas. Since the only data I’m accessing from here is e-mail, I don’t really notice any difference.

And because these are U.S. phones, there is no need to change your number. The regular U.S. phone number rings over here, albeit sometimes in the middle of the night, thanks to the nine-hour time difference.

The only downside is the international roaming charge. It might not be a big deal if you just make a few calls or if you work for a company that pays your bill. But if you’re cost-conscious and plan to use the phone a lot from overseas, you had better heed the tariffs. In Spain and in most of Europe the international roaming charge is $1.29 a minute. It’s $2.49 a minute here in Turkey and from Ghana and Saudi Arabia. Sprint users who happen to be in Russia, Chad or Kazakhstan could pay as much as $4.99 a minute. There are also data charges for e-mail and text-messaging.

There are ways to beat the system. Sprint’s world phones are unlocked, which means you can buy a SIM card in the local country and pay much lower rates. In some cases, it costs as little as 10 or 15 cents a minute for outgoing calls and nothing for incoming calls.

The Verizon phone is locked, but upon request Verizon can provide an unlocked code. There are also third parties and Internet sites that, for a one-time fee, will unlock most but not all locked GSM phones or provide you a code to unlock it yourself. I’ve used, an independent cell phone dealer to unlock phones that I and family members have used when traveling overseas.

When you’re using a SIM card you buy abroad, callers have to dial into the country where you bought the card. So if you bought a SIM card in Spain, callers would have to dial a Spanish phone number to reach you. If you then traveled to France and bought a French SIM card, they would have to dial a French number.

Another option, especially useful if you plan to travel to different countries, is to purchase a global SIM card. Sim4Travel.com and GoSim.com sell cards that can be used in most countries at rates starting at about 60 cents a minute to call back to the United States. It may not be as inexpensive as buying a local SIM card, but you get to use the same number in each country and it’s cheaper than paying international roaming rates through your U.S. carrier.

T-Mobile sells phones that can be used both on GSM networks (for a fee of course) and free via WiFi. While in Spain I ran into fellow American journalist John Biggs from Crunchgear (www.crunchgear.com), who let me try out his BlackBerry Pearl 8120 to make a free call back to the States via the hotel’s WiFi network. As long as I was close enough to a hotspot, I was able to make and receive free calls. Callers are able to call your regular T-mobile U.S. number and if you answer it from a hotspot it’s free, but if you’re using the GSM network with T-Mobile’s US SIM card, you pay international roaming rates, which vary by country.

Because almost all AT&T phones use GSM, its phones can also be used in Europe at roaming rates comparable to those of Sprint and Verizon. AT&T does offer a $5.99 plan that reduces rates by about 30 percent per minute in Europe.

Istanbul, settled by the Phoenicians in 650 BC, is home to some amazing ancient architecture but when it comes to international communications, its as modern as any place on earth.

Listen to Larry’s CBS News Podcast with Google Sr. Scientist Shumeet Baluja and National Center for Missing and Exploited Children President Ernie Allen

Working with law enforcement, analysts at the National Center for Missing and Exploited Children (NCMEC) in Alexandria, Va., spend their days doing something no one should have to do. They look at what is called “child pornography,” but the photos and videos are actually evidence of children - in some cases infants - being sexually abused.

They do this work to help rescue children who may still be in the clutches of a predator, to help catch and prosecute perpetrators and to send a message to would-be child abusers that exploiting children will not be tolerated. The online locations of suspected child pornography are reported to NCMEC via the CyberTipline by Internet service providers and members of the public. Images are submitted by law enforcement agencies across the country.

The work is emotionally draining and challenging. But thanks to some new technology from Google, these analysts now have a tool that could greatly enhance their effectiveness.

A disclosure: I serve as an unpaid member of NCMEC’s board of directors. When it comes to NCMEC’s work, I’m not objective. I passionately share the non-profit organization’s commitment to protecting children. I’m also a strong free-speech advocate, but the images they deal with are not protected by the First Amendment. Production, distribution and possession of “child porn” is illegal in the United States and many other countries.

The concept behind Google’s software is simple, but the implementation took four engineers thousands of hours over the better part of a year, according to Google’s senior research scientist Shumeet Baluja, who is the technical leader of the project.

The software allows an analyst to highlight a pattern somewhere in an image. It could be a calendar on the wall, a logo on a T-shirt, a prominent tattoo or perhaps the pattern of the carpet. It then looks for that pattern in other images and when it finds a match or a likely match it presents those images to the analyst. In some cases it will analyze the entire image to look for matches or near matches. NCMEC President Ernie Allen said the organization reviewed 5 million images and videos in the past year and more than 13 million since 2002.

Without this software, the only ways to make a match is to depend on the memory of analysts or to find an exact copy of the image with a file’s “hash mark.” But the hash mark - the digital fingerprint of a file - doesn’t follow all images. If an image is edited or compressed, for example, the hash mark changes.

We humans may be more perceptive than computers and better able to distinguish similar or unique characteristics. But computers have much better memories. As a NCMEC board member, I have heard amazing stories about analysts and police officers who have matched photos based on characteristics they remember from pictures they may have seen months ago. But I think that they all would appreciate a little help from machines.

Baluja says the technology will work even if the images are modified, if a photo has been changed from color to black and white, or if the pattern is at a different angle or position in the photo or video. It can also pick out a single pattern in a video, even if it’s a compilation of many shorter videos.

Google engineers and scientists were able to work on the project using what the company calls “20 percent time.” Google allows all of its employees to dedicate 20 percent of their work time to projects they initiate. Some of those projects benefit Google stockholders, some benefit end-users and some might wind up not benefiting anyone. This project has the potential to benefit thousands of children.

The engineers didn’t have to start from scratch. The technology is an outgrowth of the anti-piracy software Google developed to help its YouTube division ferret out videos suspected of being posted without the permission of copyright holders.

Google representatives are quick to point out that they don’t always take down copyrighted video flagged by software because in some cases there is a legitimate “fair use” case for it being posted. But what I find interesting about this is that a technology developed to protect intellectual property rights could be applied to protect children.

I’m sure that most people share Google’s motto of “do no evil.” But there are some people on this planet who are very evil toward children. Let’s hope that the efforts of these Google staffers and the hard-working people at NCMEC result in more of these evil people being sent to a place where they can no longer harm children.

If you come across videos or images of child pornography, don’t save them - that’s against the law. But do report their location to NCMEC’s CyberTipline at www.cybertipline.com

Apple last week confirmed that iTunes had outpaced Wal-Mart in January and February as the nation’s No. 1 seller of music. The Apple announcement followed an earlier report by NPD Group that compared iTunes music sales with those of major retailers. Pardon the pun but it’s not exactly an “Apples to Apples” comparison because stores typically sell albums while iTunes allows users to download one track at a time. To more or less even the score, 12 tracks were considered the same as a single album. It was only a month earlier that Apple passed Best Buy to become the No. 2 music retailer.

What’s interesting about iTunes’ meteoric rise in popularity is that it is doing very well despite some downsides to the format and the portable devices people typically use to listen to the music. For one thing, most songs purchased on iTunes are saddled with so-called digital rights management that limits what you can do with them, including what devices you can play them on. The CDs that Wal-Mart and other retailers sell don’t have DRM, so they can be ripped as MP3s and played on any digital music player.

Another difference between downloaded music and CDs is compression. Although many people can’t perceive it, there is definitely a difference between the sound of an MP3 and the sound of an uncompressed CD. What’s more, a lot of people listen to most of their music through little earbuds.

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