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U.S. public safety officials are getting ready to release more details about enhanced security for this year's Boston Marathon.

Local, state and federal agencies, the Boston Athletic Association and leaders from the eight communities that make up the marathon route are expected to reveal the new security measures.

Authorities have been meeting for months to come up with a plan to beef up security for the April 21st marathon, following last year's deadly terror attack. Three people were killed and more than 260 injured after two bombs exploded near the finish line of the race.

This year, police are expecting about 36,000 runners and up to a million spectators.

This is NEWS Plus Special English.

You're listening to NEWS Plus Special English. I'm Ding Lulu in Beijing.

We stay in the U.S.

Should shoppers turn off their smartphones when they hit the supermarket or shopping center? Or does having them on lead to better sales or shorter lines at the checkout?

Retailers in the United States are using mobile-based technology to track shoppers' movements at some malls and stores.

The companies collecting the information say it's anonymous, can't be traced to a specific person and no one should worry about invasion of privacy.

But consumer advocates aren't convinced. They say it's spying, and shoppers should be informed if their phones are being observed or monitored and then be able to choose whether to allow it.

The U.S. Federal Trade Commission held a workshop on the issue, part of a series of privacy seminars looking at emerging technologies and the impact on consumers.

FTC attorney Amanda Koulousias says the commission wants to better understand how companies are using phone-location technology, how robust privacy controls are and whether shoppers are notified in advance.

Here's how the technology works:

Your smartphone has a unique identifier code - a MAC, or media access control address - for Wi-Fi and Bluetooth. It's a 12-character string of letters and numbers. Think of it like a Social Security or vehicle identification number. In the U.S, this address is not linked to personal information, like your name, email address or phone number. The numbers and letters link only to a specific phone.

When your smartphone is turned on, it sends out signals with that MAC address as it searches for Wi-Fi or Bluetooth. Those signals can also be captured by sensors in shops that can tell a department store how often shoppers visit, how long they stay, whether they spend more time in the shoe department, children's clothing section or sporting goods, for example, or whether they stop for the window display, and then decide to move on.

Companies that provide "mobile location analytics" to retailers, grocery stores, airports and other outlets say they capture the MAC addresses of shoppers' phones but then scramble them into different sets of numbers and letters to conceal the original addresses - a process called hashing. This is how they make the data they collect anonymous.

The companies then analyze all the information those hashed numbers provide as shoppers move from store to store, or department to department within a store. Shopping center managers could learn which stores are popular and which ones aren't. A retailer could learn how long the queues are at a certain cash register, how long people have to wait - or whether more people visit on "sale" days at a particular shop.

You're listening to NEWS Plus Special English. I'm Ding Lulu in Beijing.

Finally, a piece of history revisit.

On March 18th, 1965, Russian cosmonaut Aleksei Leonov became the first human to conduct an extra-vehicular activity, also known as a spacewalk.

Leonov was outside the spacecraft 'Voskhot 2' for 12 minutes and nine seconds, connected to the craft by a 5-meter-long tether.

At the end of the spacewalk, Leonov's spacesuit had inflated in the vacuum of space that he could not re-enter the airlock.

He opened a valve to allow some of the suit's pressure to bleed off and was barely able to get back inside the capsule.

As of November 2011, Leonov is the last survivor of the five cosmonauts in the Voskhod programme of the former Soviet Union.

That brings us to the end of this edition of NEWS Plus Special English. To fresh up your memory, I'm going to read one of the news at normal speed. Please listen carefully.

That is the end of today's program. I'm Ding Lulu in Beijing. Hope you can join us every day at CRI NEWS Plus Radio, to learn English and learn about the world.