Asterisk Dialplan Syntax - 2

The s Extension
When calls enter a contet without a specific destination extension, they are passed to the s extension. eg:
[incoming]
exten => s,1,application()
exten => s,n,application()
exten => s,n,application()

The Answer(), Playback(), and Hangup() Applications
Answer() takes no argument.
Playback() application is used for playing a previously recorded sound file over a channel. Default directory for sound files is /var/lib/asterisk/sounds.
Hangup() takes no argument.