综合填空：
What do you usually use mobile phones for? Sending text messages for fun? Playing games? Well, mobile phone can do f___1____ more than that. D___2___ this year’s Asian tsunami （海啸）, mobile phones saved many l___3____. More than 10000 international phones were w___4___ when the tsunami hit. Police sent text messages to them and found more than 2000. But how? People f___5___ the signal and found out w___6___ the tourists were. So, how can s___7___ so small be so smart? Well, here’s how! When you turn the phone on, it tries to find a signal. This signal. This signal comes from the telephone network.
If you have a signal you can see it on the phone’s screen. Sometimes, if the signal is weak, i___8___ can be difficult to make a phone call. When the phone is finding a signal, it also sends a m___9____ to the telephone network. This message tells the station where the phone is. When you start to make a phone call, the telephone network tells telecommunication offices where you are. The office will find out who you’re calling then put you t___10___ to your friend!