Why in the emergency incident message than on telephone?

on April 17, scientific American website published a short essay: (according to It ‘s Better to Text Than the Call in a Mass Emergency) main content:

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in some emergency disaster and terrorist attacks, etc.), wireless communication services communications peak may occur. After a few days before the Boston marathon bombings, invited the media communications engineer to talk about this problem. Among them, the engineer when it comes to a point: wireless communication and wired communication before, without communication bottleneck problem. Under the condition of the line is busy, send text messages (SMS) to more easily than telephone contact with family and friends. The reason is:

1, relatively speaking, more light “footprints” text messages. (I understand the information was transmitted messages need less, are more likely to come out.)

2, texting is “asynchronous transmission. That is to say, if you don’t success at a time, SMS can try again to send, may delay a few seconds, but in the end is still likely to be successful. The phone is different, need real-time connection to phone. If the connection is on, means that the line is occupied by you. And busy time are more likely to not connection.

3, wireless communication, generally with the control circuit to transmit messages, rather than the “voice”. Control circuit is used to set up and end a voice calls. That is to say, even if the voice service is busy, “control circuit can also be open, so susceptible to hinder the text transmission. This is similar to the highway traffic jam, but you can run on the road shoulder, unimpeded.

the above said is SMS (short message service) service. Although the iPhone SMS and other SMS messages, use is called iMessage — this service, but it also has the best potential. Because, according to apple, the iPhone in the case of a service called iMessage — not clear automatically switch back to the SMS service. But the premise is you want to be in the setting of the iPhone open the option of using SMS to send.