DIALPLAN:

[uscita]
exten => _0XXX.,1,NoOp,zzz_Start_dialing
exten => _0XXX.,2,Dial(${LINEA}/${MSN1}:${EXTEN:1},60,g)
exten => _0XXX.,3,NoOp,zzz_After_dial_comamnd:${DIALSTATUS}
exten => _0XXX.,4,Goto(s-${DIALSTATUS},1)

exten => s-BUSY,1,NoOp,zzzBusy
exten => s-BUSY,2,Busy

exten => s-HANGUP,1,NoOp,zzzz_HangUp:${DIALSTATUS}
exten => s-HANGUP,2,Hangup

exten => h,1,NoOp(zzz_HangUp_from_h_:${DIALSTATUS})
exten => h,2,Congestion

exten => _s-.,1,NoOp,zzzEvery_other_state:${DIALSTATUS}
exten => _s-.,2,Congestion     

===============
OUTPUT (the caller hangs up first)

    -- Executing NoOp("SIP/bt101-b90f", "zzz_Start_dialing") in new stack
Urgent handler
    -- Executing Dial("SIP/bt101-b90f", "Modem/g1/4365103:04363403|60|g") in new stack
Urgent handler
    -- Called g1/4365103:04363403
Urgent handler
    -- Modem[i4l]/ttyI1 answered SIP/bt101-b90f
Urgent handler
    -- Hungup 'Modem[i4l]/ttyI1'
Urgent handler
Urgent handler
    -- Executing Hangup("SIP/bt101-b90f", "") in new stack
Urgent handler