asterisk users - Nov 2003 - which TDM to use? DID line from telco with no dial tone and no voltage

as my first project with *, i would like to replace our old 
neax2400(sds) with an * server.
i've got an X100p and a TDM400 on hand already.

for the CO lines, the X100p works ok with fxsks signaling though there 
are still strange
things happening every now and again but more testing is on the way.

my real big problem is the DID lines which our telcos call DDI lines;
(incoming calls only)
i disconnected a running DID line from our PBX and did a bunch of
tests on it and found the following:

* line from telco has NO voltage

* the port from pbx is supplying the power(voltage) but no dial tone
 
*the moment i disconnected the DID line from the PBX port,
an alarm is triggered at the telco CO

* i can attach an ordinary analog phone to the PBX PORT, pick up the 
handset and
  send (dial) 4 dtmf digits (being the last 4 digits of our DID number),
  the PBX  will bridge me to the appropriate extension phone.

* if or when the extension phone picks up, the PBX reverses the polarity 
on the line

what type of signaling should i be using for such a line?

many thanks in advance,
patrick

Hi Patrick,

You are in the UK, right (at least DDI strongly suggests that)? This is 
the commonest signalling for a DDI line on an analogue pair. The line is 
behaving just like the main exchange is a telephone. It picks up the 
line, by applying a 600ohm loop, and dials (with pulses per second or 
DTMF)  into your PBX. Your PBX port is behaving like it is a public 
exchange, with a phone attached.

Electrically, Digium's FXS card should do the job you need, but others 
will have to tell you whether * has the software features needed to make 
this work (it should certainly be pretty close).

Regards,
Steve


hkirrc.patrick wrote:
> as my first project with *, i would like to replace our old 
> neax2400(sds) with an * server.
> i've got an X100p and a TDM400 on hand already.
>
> for the CO lines, the X100p works ok with fxsks signaling though there 
> are still strange
> things happening every now and again but more testing is on the way.
>
> my real big problem is the DID lines which our telcos call DDI lines;
> (incoming calls only)
> i disconnected a running DID line from our PBX and did a bunch of
> tests on it and found the following:
>
> * line from telco has NO voltage
>
> * the port from pbx is supplying the power(voltage) but no dial tone
>
> *the moment i disconnected the DID line from the PBX port,
> an alarm is triggered at the telco CO
>
> * i can attach an ordinary analog phone to the PBX PORT, pick up the 
> handset and
>  send (dial) 4 dtmf digits (being the last 4 digits of our DID number),
>  the PBX  will bridge me to the appropriate extension phone.
>
> * if or when the extension phone picks up, the PBX reverses the 
> polarity on the line
>
> what type of signaling should i be using for such a line?
>
> many thanks in advance,
> patrick