Emergency button on iPhone 5S (how does it work)
How does the emergency button on the iPhone 5S work. How do I set it up
How does the emergency button on the iPhone 5S work. How do I set it up
What emergency button?
Are you talking about the Emergency Call button that displays before you unlock the phone? If yes...
From the iPhone Manual (you should read this)
Emergency calls
Make an emergency call when iPhone is locked. On the Enter Passcode screen, tap Emergency Call (to dial 911 in the U.S., for example).
Important: You can use iPhone to make an emergency call in many locations, provided that cellular service is available, but you should not rely on it for emergencies. Some cellular networks may not accept an emergency call from iPhone if iPhone is not activated, if iPhone is not compatible with or configured to operate on a particular cellular network, or (when applicable) if iPhone does not have a SIM card or if the SIM card is PIN-locked.
Emergency button on iPhone 5S (how does it work)