for iOS 9.1 software

Talk privately with one person: Tap , then tap Private next to the
person. Tap Merge Calls to resume the conference.
Add an incoming caller: Tap Hold Call + Answer, then tap Merge
Calls.
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.
In the U.S., location information (if available) is provided to emergency
service providers when you dial 911. Please review your carriers
emergency calling information to understand the limits of emergency
calling over Wi-Fi.
With CDMA, when an emergency call ends, iPhone enters emergency
call mode for a few minutes to allow a call back from emergency
services. During this time, data transmission and text messages are
blocked.