[asterisk-users] Learn some terminalogy before mounting thistask.

[John Faubion]

>They asked me if we want NI1 or NI2 ?? Is this a reference to the PRI ?

Yes, and just to complicate matters further, they are probably asking about
the NT-1 or NT-2 which is the Network Termination type. NI1/NI2 usually
refers to the National ISDN phase, for which the difference has generally
been eliminated. The NT-1 is a 2-wire "U" interface while the NT-2 is a
4-wire "S/T" interface. Since both NT-1 and NT-2 use the same RJ-45
connector, albeit different pins, most cards now support either interface,
and often auto-magically. I haven't used the Sangoma cards, but since the
Digium cards support this, I would expect the Sangoma cards to do the same.
Now the reason they are asking is, if your router only supported a 4-wire
"S/T" interface, then they will need to provide a CSU/DSU to convert the
NT-1 or "U" interface. Or if you already had an external CSU/DSU you might
want the NT-1 interface.

Now having said all of that, I'm actually going to recommend that you tell
them you need the NT-2 interface. Why? Demarcation. Most providers want to
provide the CSU/DSU and give you a "S/T" interface. The reasons are, if they
provide the CPE interface, they are going to use a box they know will work.
That way if you have problems, they can confirm that the circuit is good to
that point. What you do with the circuit after that isn't their concern.
Plus if you were to "accidentally" connect the 4-wire circuit directly to
120 volt AC power, you are most likely only going to fry the CSU/DSU and not
the equipment in their concentrator around the corner. Additionally, it
works both ways. If the cabinet on the corner of the block takes a lightning
strike, the CSS/DSU goes up in smoke and hopefully protects your equipment.
So just because you can use either interface, doesn't mean you should. Clear
as mud, isn't it?

John