[asterisk-users] DID to hunt group?

[Rich]

Asterisk 1.4.2

I have spent much of today trying to make a DID (from SIP GW) 
ring to 4 extensions in a hunt (roll-over) group.
Results from searching docs and forums seem to indicate it is doable
and so trivial no one includes an actual example.

I can make all 4 exts ring at once with the like of

exten => _1655,1,Ringing()
exten => _1655,2,Dial(SIP/1655&SIP/1656&SIP/1657&SIP/1658) 
exten => _1655,3,Hangup()
exten => _1655,103,Congestion()

but I want to ring the 1st ext, if it is busy then ring the 2nd, etc...

I am trying to emulate a 10-line 20 phone key system.  
The end user does not like all the phones ringing at once.

I have tried lots of combinations in extensions.conf
including the following that I would think should work...
the 2nd line never rings, just dead air, or I hear a click and dead air...
where am I going wrong

!! This did not work, not sure why
exten => _1655,1,Ringing()
exten => _1655,2,Dial(SIP/1655)
exten => _1655,103,Dial(SIP/1656)
exten => _1655,104,Hangup()
exten => _1655,204,Dial(SIP/1657)
exten => _1655,205,Hangup()
exten => _1655,305,Dial(SIP/1658)
exten => _1655,306,Hangup()
exten => _1655,406,Congestion()


!! this didn't work , I hear no ringing, 2nd call gave some wierd error about codec and slin

exten => _1655,1,Answer()       
exten => _1655,2,Dial(SIP/1655,30)
exten => _1655,3,Hangup() 
exten => _1655,103,Dial(SIP/1656,20)
exten => _1655,104,Hangup() 
exten => _1655,204,Dial(SIP/1657,10)
exten => _1655,205,Hangup() 
exten => _1655,305,Dial(SIP/1658)    
exten => _1655,306,Hangup() 
exten => _1655,406,Congestion() 


Any clues will be greatly appreciated!
Thanks,
Rich