Outgoing call problem

I am new to asterisk and I am having problems getting my out going calls to work. I have the following defined in extensions after making a outgoing call rule with the GUI.

exten=_9XXXX,1,Macro(trunkdial-failover-0.3,${trunk_1}/6${EXTEN:1},trunk_1,)

When I try to place a call it allows me to enter a 4 digit number and then gives me the busy signal. The following appears in my asterisk log

WARNING[6275] chan_dahdi.c: Unable to determine channel for data trunk_1/66440
WARNING[6275] app_dial.c: Unable to create channel of type ‘DAHDI’ (cause 0 - Unknown)

Any suggestions would be very helpful.