for iOS 9.1 software

Fast-forward: Press the center button twice quickly and hold.
Rewind: Press the center button three times quickly and hold.
Use the center button to answer or make phone calls.
Answer an incoming call: Press the center button.
End the current call: Press the center button.
Decline an incoming call: Press and hold the center button for about
two seconds, then let go. Two low beeps confirm you declined the
call.
Switch to an incoming or on-hold call, and put the current call on
hold: Press the center button. Press again to switch back to the first
call.
Switch to an incoming or on-hold call, and end the current call:
Press and hold the center button for about two seconds, then let go.
Two low beeps confirm you ended the first call.
Use Siri or Voice Control. Press and hold the center button. See
or .
Bluetooth devices
You can use Bluetooth devices with iPhone, including headsets, car kits,
stereo headphones, or an Apple Wireless Keyboard. For supported
Bluetooth profiles, see .
Make
requests Voice Control
support.apple.com/kb/HT3647