[asterisk-users] What makes TDM400 FXS Connection to TELCO go into Off Hook State?

[Jim Duda]

I've been having trouble with making outbound calls to my 
TELCO from a TDM400 card (FXS KS signalling) after upgrading
from 1.6-beta9 to 1.6.0.  The problem is completely intermittent.

When it fails, I get this message:
[Nov  9 19:12:26] WARNING[18916] app_dial.c: Unable to create channel of type 'DAHDI' (cause 0 - Unknown)

At some point, it starts working, but I don't know what is 
triggering asterisk to start working.  But I have a theory below.

I have instrumented the code with debugging and narrowed it 
down to some code in chan_dahdi where it appears to be checking
for hookstate.  I can actually resolve this issue by changing
a return code in the available function in chan_dahdi.c

This led me to look at dahdi show channel 4

It appears that when outbound calls are working, 
the Hookstate displays Offhook.

It appears that when outobund calls are not working,
the Hookstate displays Onhook.

Can anyone tell me what the normal state of an FXS line attached
to a standard TELCO should be when no call is in progress and
when a call is in progress?

Can anyone tell me what causes an FXS line attached to a
standard TELCO to transition to Off Hook state?  It seems
to me that the state would transition between off hook and
on hook as a call is in progress or idle respectively.

Thanks,

Jim

asterisk*CLI> dahdi show channel 4
Channel: 4LI> 
File Descriptor: 21
Span: 1
Extension: 
Dialing: no
Context: incoming
Caller ID: 
Calling TON: 0
Caller ID name: 
Mailbox: 100
Destroy: 0
InAlarm: 0
Signalling Type: FXS Kewlstart
Radio: 0
Owner: <None>
Real: <None>
Callwait: <None>
Threeway: <None>
Confno: -1
Propagated Conference: -1
Real in conference: 0
DSP: no
Busy Detection: no
TDD: no
Relax DTMF: no
Dialing/CallwaitCAS: 0/0
Default law: ulaw
Fax Handled: no
Pulse phone: no
DND: no
Echo Cancellation:
       128 taps
       (unless TDM bridged) currently OFF
Actual Confinfo: Num/0, Mode/0x0000
Actual Confmute: No
Hookstate (FXS only): Offhook --> Working State


My chan_dahdi.conf:

;[pstn]
mailbox=100
mwimonitor=fsk
mwilevel=512
mwimonitornotify=/usr/local/sbin/zapnotify.sh
faxdetect=incoming
signalling=fxs_ks
context=incoming
callwaiting=yes
callwaitingcallerid=yes
echocancel=yes
echotraining=no
echocancelwhenbridged=no
channel => 4

;[fax]
; FAX machine connected here
faxdetect=no
signalling=fxo_ks
context=internal
channel => 1