asterisk users - Jan 2006 - Interrupting ring to go to voicemail pickup -- How to ring after Answer()?

Hi,

I've successfully used the 'd' flag in Dial() so that when
I dial into my phone system from out there in the PSTN
network I can press the 2 key while the phone is ringing
to listen to my voicemail.

It seems that one issue is that the public providers
do not deliver DTMF, or anything, until the phone
is answered.  This is for security reasons and sounds
like a good idea to me.

So, the extension must first answer the phone.  The trouble
is then providing a ring tone to the calling party.
I stumbled upon the solution below, which seems to
work.  But there are a number of things I don't
understand, which makes the whole thing seem
really brittle.

1) Why does this not work if you leave off the Playtones()
call?  I thought Dial() was supposed to automagically
indicate ringing and provide the requsite sounds?

2) Why is the r flag reqired in the Dial() call?
If I take it out I don't hear any ringing even
though Playtones should be playing.

3) If I take the r flag out of Dial() and put
a call in to Ringing() before the Playtones()
(or maybe after, I forget)
I don't get a ring sound when calling.

4) I thought Playtones() was supposed to play
until StopPlaytones() is called.  It sure stops
playing when I get to voicemail, either by a timeout
of the Dial() or by pressing 2.  (I don't know
whether it really stops if the Zaptel is answered,
because I'm not in a position to test that at the
moment.  But I presume it will.)

Asterisk 1.2.1 extensions.conf file fragment:

exten => 2000,1,Answer()
exten => 2000,2,Playtones(ring)
exten => 2000,3,Dial(Zap/1,15,dr)
exten => 2000,4,VoiceMail(u101@default)
exten => 2000,104,VoiceMail(b101@default)
exten => 2,1,VoiceMailMain(101@default)

I'd appreciate hearing from anybody who can clue me in on
the above questions, or has any improvements or suggestions
to make to the dialplan, or otherwise wishes to throw me a
bone.

Thanks.

Karl <kop@meme.com>
Free Software:  "You don't pay back, you pay forward."
                  -- Robert A. Heinlein