Each black box is fitted with an underwater locator beacon that starts emitting a pulse if its sensor touches water, meaning it "pings" once per second for 30 days before the battery runs out.

Even though Malaysian officials declared that MH370 had crashed, no physical evidence has been found, despite a massive hunt involving seven countries. The jet carried 239 passengers and 12 crew members.

Hopes raised by debris sightings have repeatedly been crushed as the items turned out to be random sea junk such as fishing gear.

Questions:

1. When is it presumed the black box flight recorder will run out of battery power?

2. How long did it take to get the Air France Flight 447 black box from the Atlantic Ocean?

3. How many pieces of equipment are in a black box?

Answers:

1. Around April 7, or April 12 at the latest.

2. Nearly two years.

3. Two.

About the broadcaster:

Anne Ruisi is an editor at China Daily online with more than 30 years of experience as a newspaper editor and reporter. She has worked at newspapers in the U.S., including The Birmingham News in Alabama and City Newspaper of Rochester, N.Y.

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