Already heartbreaking images of grieving family and friends only become more poignant when you hear this:

Some family members and friends of the 239 people who haven't been heard from since Malaysia Airlines Flight 370 disappeared Saturday say they've been calling their loved ones' cellphones and hearing rings — though no one picked up the calls.

Could those rings be a sign, they wonder, that the phones are still working — which in turn could mean that the people they belong to are safe?

Sadly, the rings are not evidence that the worst hasn't happened.

talked to us this morning about what happens when cellphone calls are made.

"When a customer calls another number," he said, "the carrier has to decide what to do next."

Basically, it starts searching for the phone that's being called.

While the phone company's doing that, it sends a ring — or two, or three, or more — to the person who initiated the call. The phone company does that, Kagan said, "so that the customer doesn't hang up" while the search for that other phone is underway.

This happens to him quite frequently, Kagan told us. "My wife will call me and say she heard it ring two or three times. But I picked it up on the first ring [that he heard]." She was hearing the "rings" that the cellphone carrier sent while it was searching for his phone.

How long it takes to either find the other phone or determine that it can't be reached depends on many factors. They include whether the person making the call is trying to reach someone whose phone is part of a different network and whether the person being called is in a different country. Such variables can add to the time it takes to either complete the call or disconnect.

When a carrier can't find the phone that's being called, any one of several things may happen:

-- The call might be dropped.

-- The call might go to the person's voicemail.

-- The call might go to a recorded message saying it couldn't be completed.

"There's not a standard way" that such uncompleted calls are handled, Kagan said.

Flight 370 was on its way from Kuala Lumpur, Malaysia, to Beijing when it disappeared. The airline says 154 of those on board were from mainland China or Taiwan. "According to Chinese media," theMirror writes, "19 [Chinese] families have signed a joint statement confirming they made calls which connected to the missing passengers but without an answer."

Kagan says he understands why grieving families might get some comfort from or be confused by the "rings" they've heard. But he wishes their expectations weren't apparently raised needlessly.

"I hate that they have hope" because of this bit of technology, he said.

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