asterisk users - Nov 2003 - telco access ?s -- PRI, T1, POTS?

Hi guys,

I'm new to the telco game and still pretty new to Asterisk, although 
I've been using it for a couple of months now and like most of what I 
see.  At my office, we've got a small two extension setup w/ two Digium 
cards for a single FXO line and three FXS extensions, but I'm also 
working on designing a larger installation for a customer which will 
involve ~16 analog handsets that I'll be running through a Rhino 
Equipment channel bank to a Digium T1.  My question is all about what 
type of phone service would be recommended for my local provider.

I purchased a CAC FXO channel bank to interface with a second Digium T1 
card that I've got, and ran some small scale tests on that which seemed 
to go fine, and I'm sure this solution would be *sufficient* for the 
customer, but I know he would like to be able to do DID, which, from 
conversations w/ SBC in my area, I've discovered requires something 
other than POTS.  We'll be looking to have roughly 10-12 phone lines for 
both inbound and outbound (as you'd have in the POTS world), or w/e the 
PRI, etc. equivalent would be.

So the real question is, from all of your experience, assuming my local 
telco can provide me w/ any possible solution, what would you all 
recommend I choose?  Some sort of fractional T1 line w/ DID trunks for 
incoming and POTS for outbound calls (pardon my description of these 
solutions if they are inaccurate--again, I'm new to the game) or what 
else? 

The other main point I should make is that both the customer and myself 
are interested in a solution where we could, in an emergency, or in the 
event my configuration of Asterisk is inadequate, switch back over to a 
situation where we could at least place and receive all calls using the 
analog handsets.  (E.g., from what I know about this stuff, I suppose I 
could plug the Rhino FXS channel bank into an incoming T1 line which 
would then split all the lines into analog which my phones could then 
plug right into--of course, if I went w/ a straight POTS solution, we 
could obviously just plug 10-12 of the analog handsets into the lines 
and at least answer the phones (albeit in a haphazard manner)).

I apologize for the length of this question, but I figured some of the 
knowledgeable people on this list would've had some experience in these 
areas.

Thanks,

jl

On Tue, 2003-11-18 at 11:04, john lawler wrote:
> Hi guys,
> working on designing a larger installation for a customer which will 
> involve ~16 analog handsets that I'll be running through a Rhino 
> Equipment channel bank to a Digium T1.  My question is all about what 
> type of phone service would be recommended for my local provider.
> 
> I purchased a CAC FXO channel bank to interface with a second Digium T1 
> card that I've got, and ran some small scale tests on that which seemed
> to go fine, and I'm sure this solution would be *sufficient* for the 
> customer, but I know he would like to be able to do DID, which, from 
> conversations w/ SBC in my area, I've discovered requires something 
> other than POTS.  We'll be looking to have roughly 10-12 phone lines
for
> both inbound and outbound (as you'd have in the POTS world), or w/e the
> PRI, etc. equivalent would be.
> The other main point I should make is that both the customer and myself 
> are interested in a solution where we could, in an emergency, or in the 
> event my configuration of Asterisk is inadequate, switch back over to a 
> situation where we could at least place and receive all calls using the 
> analog handsets.  (E.g., from what I know about this stuff, I suppose I 
> could plug the Rhino FXS channel bank into an incoming T1 line which 
> would then split all the lines into analog which my phones could then 
> plug right into--of course, if I went w/ a straight POTS solution, we 
> could obviously just plug 10-12 of the analog handsets into the lines 
> and at least answer the phones (albeit in a haphazard manner)).
Your wish for DID and the wish to remove asterisk from the loop in case
of failure are going to clash with each other. DID can be delivered via
E&M wink, but this will require a machine on your end that will work
with that signaling. E&M wink basically is like having the telco dial an
extension in your PBX for your caller. 

PRI would not allow you to just swap out to analog phones at all as the
Rhino will not understand the signaling on the 24th channel.

You would be best to get very familiar with this setup, and go with the
frac T1. If you don't feel comfortable deploying yet, then you aren't
ready to deploy. I don't wish to seem mean here, but this is a critical
component of your clients business life and if you can't pull it off,
then you don't have any business experimenting on your customers money.
Read the archives of a similar fellow who had a asterisk system not work
out for his client. 

Right now, I'd say a fair knowledge of the internals of asterisk should
be a requirement for anyone selling asterisk systems into a client site.
This would help you go far in justifying your knowledge level to your
customer. If you could even point to your name in the credits file, this
would be a very good selling point to your clients. If you don't want to
get dirty in the coding, thats fine, but you should be able to debug
sections of the code when you find a problem.

So far I know there are several vendors on this list that have their
names in the credits file, and are active here. If you don't feel you
can go it alone, you would also do well to find one of these vendors and
see if they can be contracted out on a contingency basis to cover what
you don't know.

BTW, I am not a vendor. 

-- 
Steven Critchfield  <critch@basesys.com>