On Oct 20, 2005, at 1:15 PM, Michaël Gaudette wrote:
I'm a computer engineer with basic knowledge of telecom. Actually,
less then basic to be honest. I've been playing around with
Asterisks for a few weeks with 2 FXS and 2 FXO cards, and having a
bit of fun making a home PBX. I'd like to know how I could apply
this new knowledge to, for example, developping a PBX solution for
this following hypothetical company:
Welcome! Asterisk can definitely do what you are looking for, and
save this hypothetical company money in the process, I bet. (The T1
should be cheaper than 72 analog phone lines, if that's how they are
doing it...).
- Exactly 72 employees each with a direct telephone number that
goes directly to their phone. Ex: Bob is 444-555-6666 and Lisa is
444-555-6667. Let's say they don't have a PBX yet.
- Statistically, the max number of outside lines ever busy at the
same time was 24 (how conveniently T1-like)
Well, this is a hypo, but 24 simultaneous calls is a bit close to the
maximum for comfort. I would want a few extra lines available for
growth, unexpected peak calling usage, etc. (What happens in an
emergency/serious problem at multiple customers, or anything else
unexpected where call volume spikes?)
. They don't want to change their business cards, so 444-555-6666
should still reach Bob, but now by going to the PBX first. The PBX
should recognize that the call was made to 444-555-6666 and switch
it to Bob automatically. Bob should see the Caller ID of the
caller on his phone.
Yes, this will easily work via the T1. Your Provider will send the
DNIS information when the call comes in. Normally they provide the
last 4 or last 7 digits of the dialed number (Choose seven. We used
to have 4, but we ended up with two numbers that had the same last 4
digits.) Asterisk uses this info to route the call to the correct
phone. CallerID will come in, too, but a T1 can only provide CallerID
Number, not name. A PRI is necessary for CallerID Name.
This is it. Conceptually, not very complicated. My guess is I
would need (and this is where I need confirmation from somebody in
the know):
- Asterisk PBX
- A Digium T1 line for a connection to the phone service provider
(I'm in Canada, so let's say Bell Canada for argument's sake)
Yes, but you could use a Sangoma card, too.
- A T1 line from Bell Canada (or other)
- Something (not sure what) on the outside to connect to those 72
phones (3 T1 cards internally connecting to a wire panel, in turn
connected to 60 phones?
You could use:
1.) IAX or SIP softphones
2.) SIP Hardphones (Cisco, Polycom, etc.)
3.) Analog phones connected to a Channel bank, connected to a T1 card.
If you choose option 3, you could buy a quad-span T1 card from
Sangoma or Digium and use one port for the incoming T1 or PRI and the
other three for extensions. Then if you need to add another incoming
T1 for incoming/outgoing calls or extensions, you could add another
T1 card. you could also use ADSI screenphones if you choose, though
many would prefer SIP hardphones at that point.
Is this it? Do I need anything else?
Well, experience, patience, and a working dialplan will all be
important! I would personally recommend a GUI configuration tool,
such as AMP, IPManager, or something of the like. This, of course,
depends on your preferences, though, so feel free to hand-code if you
so desire.
For something like this as your first serious production install, you
might want to consider hiring a consultant.
Follow-up questions:
a) Is is possible to have 72 numbers associated to a single T1
(more numbers than lines)?
Yes. You will have to port the existing analog numbers to the T1,
which will disconnect the existing analog line. What you might want
to do is start with one phone number and port it to the T1. plug the
user's phone into the asterisk server, and make sure it works as
expected. Then port another ten numbers and make sure that they all
work. Keep porting numbers in groups of ten, twenty, or whatever you
feel comfortable. That way if something doesn't work, you will only
have 1, 10, or however many people whose phones are not functional,
not all 72.
b) Will Asterisk be able to recognize (and how?) which number the
call came on, so it can run the right dial plan?
Yes, see comment about DNIS above.
c) This migth be a Canada-specific answer, but I'll try: When
leasing a T1 line, does the regional code have to be based on
geohraphy? Could I have a T1 with 416 (Toronto) numbers located in
Montreal (514)?
Not certain. We have phone numbers from throughout the state (all in
the same Area Code) ported to our T1, so a customer can dial a local
number but the call still comes in to our central office. Whether
this is possible between area codes, though, I don't know.
I sure hope my questions weren't too "newbie-like". I fear they
are, but I've really tried finding the info on the web. I
certainly wouldn't be insulted if the only reply I got was a link
to a decent Web site explaining all this.
No, but again, you might want to consider hiring a consultant before
you tackle something like this. At the very least, take it slowly as
I suggested above.
Tom
------------------------------------
Tom Rymes
Cascade Link Systems
www.cascadelinksystems.com
(603) 375-1414
Technology solutions for small & medium sized businesses
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