A recent traveler to France wondered why he couldn't use his credit card at automated points of purchase, such as gas stations or toll booths, where there was no human attendant.

It's a simple reason, with a complicated back story.

While the United States clung to magnetic stripe credit cards — swipe and sign — other countries relied on cards with chips (so called EMV cards, after Europay, Mastercard, Visa).

"The reason EMV became a standard was it was more secure,"   said Joe Cortez, of Nerd Wallet, a financial consumer website. "It generates a unique code when the card is used, unlike the information on a magnetic stripe card, which doesn't change and makes it easier to create a counterfeit card."

Having a magnetic stripe card is basically giving someone a "key to your house," he said.

Chipped credit cards came to the United States several years after they were introduced in Europe; the first version of EMV was introduced there in 1994. It wasn't until October 2015 that U.S. businesses faced liability for fraudulent activity if they didn't have the terminals to accept chipped cards.

Here's the issue, though: Chipped cards come in a couple of familiar flavors: chip and signature or chip and PIN (personal identification number).

In the first case, you pay and sign. In the latter, you input a PIN, not unlike what you do with a debit card. Because few merchants compare a customer's signature to an ID — even if they do, a well-practiced fake scrawl can be hard to detect — the PIN card is said to be more secure.

When the U.S. credit card industry finally implemented the chipped card, it was chip and signature. Merchants, it was said, were concerned about the customer experience. Chipped cards take longer to process already, and adding a PIN wasn't in the cards, so to speak.

In the rest of the world, chip and PIN is prevalent. But travelers were assured that their chip and signature cards should work even in unstaffed kiosks.

Cortez recommends taking at least two kinds of credit cards, because unexpected problems (besides the signature issue) can arise. If a credit card company suspects fraud, it will cancel or freeze a card. That is a good reason to alert your credit card companies that you will be traveling. (You often can do that online.)

Matt Schulz, at CompareCards.com, a credit card marketplace and information site that's part of Lending Tree, thinks "your best move is to get yourself a chip and PIN-compatible card before you travel" abroad.

"International travel is stressful enough as it is. If getting a chip and PIN can eliminate a couple of headaches and variables from your trip, to me, it's worth the … annual fee."

Some cards do not charge foreign transaction fees.

Other cards, available through credit unions, sometimes require you to join an organization before you are eligible. You can find lists at several sites, including Credit Card Insider, Wallet Hub, and CreditCards.com.

Some credit card companies issue you a PIN — for cash advances. Check whether your credit card company can offer you a PIN for international travel, which has nothing to do with a cash advance (and its interest fees).

And there is always cash.