[Asterisk-Users] extensions.conf dial plan

[Georg P. Israel]

Dear Asterisk users,

I was wondering if anybody can tell me how to define a dial scheeme such
that an incomming all first rings for e.g. 20 seconds on one set of
phones and then after this time extends it's range onto a bigger set of
phones.
Basically, this is easy,

I can do this in the "extensions.con" with 


[ISDN-in]
exten=> 6201030,1,setcallerid("${CALLERID}" <${CALLERID}>|a)
exten=> 6201030,2,dial,${UserGroup1}|20|t
exten=> 6201030,3,dial,${UserGroup1&UserGroup2}|60|t
exten=> 6201030,4,Voicemail2(u6201030)
exten=> 6201030,5,hangup
exten=> 6201030,302,Voicemail2(b6201030)


But here is on major problem,

in step 2, after 20 seconds, the call on the phones in Group1 will be
terminated and then restarted in the bigger group (Group1&Group2).
The problem with this is, during the transition is a time gap of a view
seconds on the phones from Group1. That means, if I lift up the head set
during this gape, then I can loos the calls on those phones.

Hence, I was wondering if I can set the dial proceadure such, that I
have the calls for 80 seconds on the phone Group1, and after 20 seconds
additionally on the phone Group2 without any interruption of the ringing
on the other phones.

Best regards

Georg P. Israel