handshake
機体の捜索は3週目に突入しました。以下は誰もが思った疑問についての記事。
Why didn't missing jet passengers use their cellphones?
In the age of smartphones and social media, one question surrounding the disappearance of the Malaysian airliner is why none of the passengers tried to contact relatives, as they did during the 9/11 attacks. Even the absence of phone calls or emails from those on board the Malaysia Airlines Boeing 777 could provide clues for investigators struggling to solve one of the greatest mysteries of modern aviation.
It may indicate that the plane was flying too high or was over water, or that the passengers were unconscious, possibly due to a change in cabin pressure.
Experts say the chances of the 239 people on board Flight 370 being able to use their mobile devices would have been better the closer they were to a mobile network on the ground. Many are sceptical that the passengers or crew would have been able to establish and maintain a call using cellphones while travelling at speed, particularly at cruising altitude.
For mobile phones to be used, there must be a contact between the handset and the network -- known as a handshake.
This requires a strong enough signal from both a transmission tower and the phone. Theoretically, 23,000 feet (7,000 metres) and 45,000 feet are a cell range that terrestrial mobile network could work with, said Singapore-based telecommunications consultant Koh Chee Koon, referring to unconfirmed reports of changes in the plane's altitude after it lost radar contact.
http://jen.jiji.com/jc/eng_afp?k=20140320031043a
こういう用法のhandshakeは知りませんでした。基地局との電波上の「応答確認」のことをいうようです。（UG）
