a sip x-lite softphone
extension.conf
exten => _telszam,1,Answer()
exten => _telszam,2,Dial(SIP/100,20,m)
exten => _telszam,n,GotoIf($["${DIALSTATUS}" = "BUSY"]?3)
exten => _telszam,n,Hangup()
exten => _telszam,3,Dial(SIP/200,20,m)
exten => _telszam,n,Hangup()