asterisk users - Apr 2003 - Unexpected behavior of X100P and * in no-dialtone situations

I have some strange behavior happening with call flow when analog 
line errors are encountered.  This may be due to the way that the 
X100P detects "busy" signals, or it may be something in the software. 
Could someone with more in-depth knowledge make a comment on the 
items below?

My dialing logic says "dial local area code numbers out of the analog 
line, and if the analog line is broken, play a fastbusy signal.  If 
the analog line is simply already occupied, push the call out of 
iconnect."   I use macros to play the busy signals and dial through 
iconnect, but that is more or less irrelevant to the question I have.

The snippet of extensions.conf:

exten => _1503.,1,Dial(${DIALOUTANALOG}/${EXTEN:1})
exten => _1503.,2,Macro(fastbusy)
exten => _1503.,102,Macro(nufone,${EXTEN},70)


I disconnect the wire from the back of the X100P.  This should (in my 
mind, at least) create an error condition.  But here is the output on 
the console when I run that routine:

.
.
.
     -- Executing Dial("SIP/2205-fae6", "Zap/1/5034547151")
in new stack
NOTICE[18449]: File app_dial.c, Line 476 (dial_exec): Unable to 
create channel of type 'Zap'
   == Everyone is busy at this time
     -- Executing Macro("SIP/2205-fae6", 
"dialiconnect|15034547151|70") in new stack
     -- Executing SetCallerID("SIP/2205-fae6",
"14163727244") in new stack
     -- Executing SetCIDName("SIP/2205-fae6", "John Todd")
in new stack
     -- Executing Dial("SIP/2205-fae6", 
"IAX/jtodd@nufone/15034547151|100|T") in new stack
DEBUG[18449]: File app_dial.c, Line 365 (dial_exec): SIMPLE DIAL (NO URL)
.
.
.

As you can see, it does not think that the error condition is an 
error condition; Asterisk merely thinks the line is busy and the call 
is handed off to the +101 priority.  Should Asterisk interpret a 
no-dialtone (in fact, no line) situation as "busy" and jump to the 
+101 priority, or should it jump to the next priority with an error? 
(In my case, it would play a fast busy or congestion tone.)  The 
reason I ask is that I'd like to put some pre-recorded announcements 
in where I currently have "fastbusy" being called, and if I never get 
handed off there I can't distinguish between a busy signal and an 
error on the line, and thus the error messages become fairly useless.

JT