ISDN, caller ID and leading zero

oscarBravo

Caller ID units attached to my ISDN line don't display the leading zero for national calls. This is a bit of a nuisance, for two reasons: first, I can't tell at a glance whether I'm getting a call from (096)12345 or (094)9612345, as I'm in the 094 area code. Second, my phone lets me call back missed numbers with one button - doesn't work if the missed number is missing the leading zero, so I end up having to write the number down and dial it manually.

The phones are PSTN handsets (and a fax/answer machine) connected to the analogue ports of an Eicon Diva ISDN "modem" - is there a setting on the Diva that controls this?

iano

You will have to check the manual and/or FAQ for your specific TA.

Eicon is well aware of the leading zero issue on Euro-ISDN, their Diva Client for Windows NT Reference Guide contains the following:
"The Euro-ISDN protocol suppresses the leading zero when sending. Therefore, the
server will normally not be able to call the client back in Shorthold mode. However, with the callback prefix 0, the complete call number is dialed. "

Perhaps there is an equivalent setting for your TA.

fatherdougalmag

Is it a Diva T/A ISDN Modem or a Diva 852 ISDN T/A?

oscarBravo

Diva TA ISDN Modem. Serial port, ISDN port, two PSTN ports.

The only way I have of configuring it is through the at@menu interface, and I can't see any settings in there relating to callback prefixes.

fatherdougalmag

Hi,
As far as I know there's no existing AT command or setting which you can use to add the prefix at that level. Is there any facility within your caller ID box to add it? Maybe if it's a known ETSI/EuroISDN quirk the Caller ID box might provide something.

You could always try contacting customer support (free) with your query for a definitive answer.

oscarBravo

No caller ID box per se - just the built-in facility on a DECT phone and a fax/answer machine. I doubt they'd be remotely ISDN-aware, since they're PSTN devices hanging off the analogue ports of the Diva.

I'll try the query route - thanks for the link - I'll post back with results, if any.

oscarBravo

Nice polite email from Eicon:

The caller ID is presented to the Diva T/A and the phone by the switch (whether Public Exchange or PABX). The Diva T/A does not do anything in regards to this.

If the call is from outside the area code and there is no leading zero, and you have a direct line, it means that it is the Public Exchange that doesn't display the leading zero. In this case (if you have a direct line), you need to speak to your line provider.

If you have a PABX in between, it is your PABX manufacturer you need to speak to.

So it's back to Eircom. I suspect the problem may be with the configuration of the Airspan pseudo-ISDN WLL doohickey. Problem is, I haven't the faintest idea where to start with trying to get Eircom to do something about it. 1901? I don't think so...

fatherdougalmag

Don't give yourself further grief. I suspect Eircom have better things to be doing than worrying about leading 0's

A quick look at the relevant ETSI spec (ETS 300 102-1) reveals that the box may very well be able to determine whether or not a prefix should be added.

When a call arrives it is contained within a Q.931 SETUP message. This SETUP message contains information about the call. The different bits of information are carried by information elements. One such information element is the 'Calling Party Number'. Within this information element there is a field called 'Numbering Plan' which tells you a bit about the number. This tells you a bit about the number itself. For one such plan ('unknown') it says that that prefix or escape digits might be present - they might also be absent.

I guess Eicon could add the feature by allowing you to specify the length of a local number and a prefix. So when a call arrives and it's number is > the length you specified the prefix is added automatically for you. But then, they'll probably just see this as an enhancement and not as a bug so it's unlikely they'd take it on.

All the same, I wonder why the leading 0 is stripped anyway. Seems a bit silly in the first place.

oscarBravo

Originally posted by fatherdougalmag
Don't give yourself further grief. I suspect Eircom have better things to be doing than worrying about leading 0's

Nah, you're right - I've survived this long without too many grey hairs!

I guess Eicon could add the feature by allowing you to specify the length of a local number and a prefix. So when a call arrives and it's number is > the length you specified the prefix is added automatically for you. But then, they'll probably just see this as an enhancement and not as a bug so it's unlikely they'd take it on.

I don't think it'd work anyway, given the mixed state of numbering around these parts. I'm in the 094 area, just outside the 096 area. 096 (Ballina) numbers are still 5-digit, while 094 numbers are 7-digit. Worse again, some 094 numbers (Ballyhaunis) start with 96 - so they're indistinguishable from Ballina numbers. They all appear as 7-digit numbers starting with 96.

All the same, I wonder why the leading 0 is stripped anyway. Seems a bit silly in the first place.

Yup. As I said, I reckon it's likely to be an Airspan issue - it's not entirely ISDN-compliant as it is.

iano

As I stated in my earlier post, Eicon are well aware of the "leading zero" issue on Euro-ISDN and have a parameter/workaround for their server-based products.

Given this, the reply from their tech support was less than wonderful!

fatherdougalmag

Yes but the product ranges are completely independent as are the code bases and the development groups! And, as far as I know, the Diva ISDN T/A is EOL. They have a different T/A product now - Diva 852 - which is different yet again. I'm not sure how that behaves or if there is any workaround available on that.