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CompTIA A+ Certification All-in-One Exam Guide

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AMBER Alerts. Many of these emergency broadcast system alerts also force

your phone to emit a very loud sound or vibrate incessantly in order to get

your attention.

EXAM TIP A software development kit (SDK) is used to write apps.

Don’t confuse it with the Android application package (APK), which is a

package file containing the assets compiled from an Android app’s code, then

used to install the app on an Android device.

While modern smartphones can place 911 calls effectively, the old 911

system relied on the Public Switched Telephone Network (PSTN) to trace a

call and determine its location, in order to dispatch emergency responders to

the correct address quickly. This was problematic with mobile devices, so

legislation was passed (the Wireless Communications and Public Safety Act

of 1999) requiring carriers to be able to pinpoint the location of a mobile

device, such as a smartphone. The Enhanced 911 (E911) system uses GPS

and cellular networks to triangulate the location of a phone by its distance

from cell towers, its transmission delay time, and other factors.

Mobile Payment Service

As smartphones and other mobile devices have become so much more

commonplace in our daily lives, we’ve become very reliant on them to store

our personal and sensitive information such as passwords, credit card

numbers, financial documents, receipts, and more. Over time, smartphone

manufacturers, as well as merchants, realized that the next logical step was to

enable you to pay for goods and services simply by scanning your

smartphone or using an app.

The app connects to your bank information and automatically transfers the

funds from your bank to the merchant. This feature is called mobile payment

service. Near Field Communication (NFC) applications refine the process

further: simply place your device on or near the special pad at the register in

order to authorize payment to the merchant. (See “NFC,” later in this chapter,

for the scoop on these tiny networks.)

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