From March 9: Sister of MH370 passenger calls brother and phone keeps ringing

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7. When my cell phone battery is dead if someone calls it they hear a ring

Of course, my dead phone does not ring. Same when my husband's phone battery is dead and I call it. I hear a ring, he hears nothing.

Cell phones do not work the same as landlines.

A phone “rings” when its network indicates an incoming call and the phone thus alerts the user. For landline telephones, the call signal can be an electric current generated by the switch or exchange to which the telephone is connected. For mobile phones, the network sends the phone a message indicating an incoming call.

A telephone “ring” is the sound generated when there is an incoming telephone call. The term originated from the fact that telephones originally had a ringing mechanism consisting of metal bells and an electromagnetically-driven clapper, producing a ringing sound. The electrical signal powered the electromagnets which would rapidly move and release the clapper, striking the bells. This electromagnetic bell system is still in widespread use. The ringing signal sent to a customer's telephone is 90 volts AC at a frequency of 20 hertz in North America. In Europe it is around 60-90 volts AC at a frequency of 25 hertz. Some non-Bell system party lines in the US used multiple frequencies (20/30/40 Hz, 22/33/44 Hz, etc.) to allow "selective" ringing.
http://en.wikipedia.org/wiki/Ringtone#Background

When you place a call, hit the send button, and your phone starts to ring, it "doesn’t mean it is ringing on the phone of the person you are calling," says wireless analyst Jeff Kagan.

"What it means is the network is at work, trying to locate the party you are calling," he says. "It rings once, twice, three times, and if it finds the phone, it delivers the call. If it doesn’t find the phone, then the call is disconnected."

Family members over there are hearing the [ring] tone and they are hoping, but this is not a sign of anything. This is just how the networks work," Kagan says.

That ringing sound to which we're so accustomed is actually a psychological trick, meant to keep us on the line while the network works to locate the other phone.

"The ringing sound is generated by the originating carrier's switch while the network sets up the call," a CTIA-The Wireless Association spokesperson tells Mashable. "This keeps callers from abandoning the call when they hear no sound. The ringing sound has nothing to do with the actual 'ringing' of the called party's device."
http://mashable.com/2014/03/11/why-malaysia-airlines-passengers-phones-ring/