- When the command is issued with <n> > 0 and <tout> > 0, the <n>
ringing tone is played for <tout> seconds and stored as default
ringing tone.
- If command is issued with <n> > 0 and <tout> = 0, the playing of
the ringing is stopped (if present) and <n> ringing tone is set as
current.
- If command is issued with <n> = 0 and <tout> > 0 then the current
ringing tone is played.
- If both <n> and <tout> are 0 then the default ringing tone is set as
current and ringing is stopped.