[Asterisk-Users] which TDM to use? DID line from telco with no dial tone and no voltage

[hkirrc.patrick]

Hi again,

thanks a million for the info.

regards,
patrick

Steve Underwood wrote:

> Hi Patrick,
>
> From memory (I haven't lived in the UK for 11 years) the electrical 
> characteristics are pretty much the same: -48V, 35mA loop current, 
> 600ohm complex impedance. One key difference is an extension needs to 
> ring, but a DDI line does not. The different cards you see used may be 
> because the DDI port has no ringer, or it may be a marketecture issue 
> - they can probably squeeze more money out of the customers for the 
> DDI ports. If they get full approvals only on the DDI card, then only 
> a pricy DDI card can be used to attach to the DDI lines.
>
> Regards,
> Steve
>
> hkirrc.patrick wrote:
>
>> Hello Steve,
>>
>> You are exactly right about the DDI line and thank you for clearing 
>> up the 600 ohm loop.
>>
>> Can you tell me other electrical details?  It's just that all the 
>> PBXes (that I know)  uses
>> different cards for DDI lines and analog extension lines and since 
>> the CO normally or at
>> least, expected to be much further away than an extension phone, I 
>> was wondering if  there's
>> a difference in the electrical requirment.
>>
>> thanks again,
>> patrick
>>
>>
>> Steve Underwood wrote:
>>
>>> 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
>>>
>>>
>
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