How to implement a call to a group in Asterisk and expand the group of subscribers in a few seconds?

Question

linux

Please tell me how to correctly implement the following functionality:
The call is routed to a group of operators 1,2,3 in case of no answer in 30 seconds, operators 1, 2, 3 continue to ring and the phones of operators 4, 5, 6, 7 start ringing .Request
a solution like:

Answer;
Dial (SIP/1&SIP2&SIP3); 
Dial (SIP/1&SIP2&SIP3&SIP/4&SIP5&SIP6&SIP/7);

or

Queue(operators123);
Queue(operators1234567);

Do not offer.
All operators are static SIP subscribers. All phones should ring at the same time.
I would like to see something like best practices.

Answer 1

Definitely through the local channel.
asterisk.ru/knowledgebase/Asterisk+local+channels
In addition to Rsa97 .
You can send a call to another context, so it will be clearer. According to your TOR it will look like this:

[new_context]
exten => s,1,Wait(30)
exten => s,n,Dial(SIP/4&SIP/5&SIP/6&SIP/7)

Answer 2

exten => _Wait-XX-XXX,1,Wait(${EXTEN:5:2})
same => n,Dial(SIP/${EXTEN:8})

exten => 100,Dial(SIP/101&LOCAL/Wait-15-102&LOCAL/Wait-30-103)

Answer 3

torr2009, what exactly do you dislike about your version?
Dial with the t option, then a new Dial with more employees.