[Asterisk-Users] OT: BRI ISDN question

[mike at pellatt.co.uk]

Well... I'm not an ISDN guru but a mere user. Though I'm sure the man in the street would consider me a guru...

Be careful over ISDN2e from BT and how you order it. The following options ARE available:

i) one number hunted over multiple ISDN2e lines
ii) A DDI range (planning fee £200) hunted over multiple ISDN2e lines
iii) one number delivered over a single ISDN2e line
iv) An MSN range (up to 10 numbers) delivered over a single ISDN2e line

what is NOT available is:
i) an MSN range delivered over multiple ISDN2e lines.

What this means in english (!!!) is that if you want more than a single number delivered over more than one line you're into the £200 planning fee - per number range. And if you started with a range of MSN numbers delivered on a single line, and you want those same numbers delivered over a further line or lines, in general you can forget it, since BT allocate DDI ranges from a different pool than MSN ranges (for administrative, rather than technical reasons I believe). They'll probably not be contiguous anyway, so you'd be into £200 per number (each being a range of one !!) even if you could do it.

Now..............
ISDN2e can be delivered in 2 ways - "system" AKA "point to point" or "point to multipoint".
Point to multipoint allows multiple devices to be connected to the bus, and just one of them to respond to a particular number. For me, I have an Network Alchemy Cybergear Gold and an Asustek P-IN100-ST-D in one of the computers both connected to the ISDN2e line. I (currently) use isdn4linux to deflect certain calls without the 2 D channels being occupied. The Gold responds to all the MSNs bar 1, on which I am playing with * (having only discovered it a week or so ago and being MOST impressed). Point to multipoint is ONLY available on single-line ISDN2e. Once you start hunting over multiple lines, PtP is the only delivery on offer - and in this case only one item of CPE can be connected to the line.

These 2 presentations are the same physical interface - it's just the signalling that differs. The Gold, for instance, has a configuration option to choose PtP or PtM. Can't remember how isdn4linux handles it though. Or even if it needs to !! See, said I wasn't a guru.

Hope all this waffle helps. Oh yes, for single line you can specify PtP (System) or PtM at order time.

Mike Pellatt
 

> -----Original Message-----
> From: wipeout [mailto:wipeout at linuxmail.org]
> Sent: 22 May 2003 15:44
> To: asterisk-users
> Subject: [Asterisk-Users] OT: BRI ISDN question
> 
> 
> I am going to try and use a passive AVM fritz BRI card for my 
> * setup..
> 
> Here is the thing.. I need to order my BRI from BT.. The 
> service that looks to be the one to use is what they call 
> ISDN 2e becasue this has the option to setup hunt groups 
> across multiple ISDN2e lines so I could add another line 
> later to get 4 channels..
> 
> According to the BT website in order to use the hunt grouping 
> across multiple lines the line has to be installed in what 
> they call "system access" using a "T" interface which can be 
> seen here..
> http://www.bt.com/isdn/isdn2e/getting_started/line_setup.htm
> 
> I have no idea what this is becasue I am not an ISDN guru.. 
> so I am asking the question.. Can an AVM card (or 2) be setup 
> to work in this "T" interface configuration or will I be 
> forever limited to 1 BRI setup with an "S" interface??
> 
> Thanks..
> -- 
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