asterisk users - Oct 2005 - txfax (app_txfax) sending issue

Hi All,

With spandsp.0.0.2 pre20 installed I can't seem to send faxes with 
tx_fax over a Zap channel (POTS). rx_fax works just fine so no issues 
with libtiff and (presumably) libxml2.

Basically I get 'slow carrier up' and 'slow carrier down'
together with
accompanying beeping noises until tx_fax times out and hangs up.  This 
could quite possibly be a PEBKAC or n00b problem since I'm relatively 
new to Asterisk.

--------- snippet: extensions.conf ---------

exten => _8NXXXXXX,1,Set(FAXFILE=/var/spool/asterisk/fax/sendfax.tif)
exten => _8NXXXXXX,2,Set(LOCALHEADERINFO=Company name and department)
exten => _8NXXXXXX,3,Set(LOCALSTATIONID=Company name)
exten => _8NXXXXXX,4,TXFAX(${FAXFILE}|caller)

--------- // extensions.conf ---------


--------- snippet: * console ---------

*CLI>     -- Executing Set("SIP/rec1pub1-af67", 
"FAXFILE=/var/spool/asterisk/fax/sendfax.tif") in new stack
    -- Executing Set("SIP/rec1pub1-af67",
"LOCALHEADERINFO=Company name
and department") in new stack
    -- Executing Set("SIP/rec1pub1-af67", "LOCALSTATIONID=Company
name")
in new stack
    -- Executing TxFAX("SIP/rec1pub1-af67", 
"/var/spool/asterisk/fax/sendfax.tif|caller") in new stack
Slow carrier up
Slow carrier down
Slow carrier up
Slow carrier down
Slow carrier up
Slow carrier down
Slow carrier up
Slow carrier down
Slow carrier up
Slow carrier down
...

--------- // * console ---------


Could anyone tell me what I might be missing or what I have to look for?

Thanks in advance.