[Asterisk-Users] Re: T1 questions follow-up

[Tom Rymes]

On Oct 20, 2005, at 2:36 PM, Michaël Gaudette wrote:

> Tom, Thank you!  This was all hypothetical, because I'm trying to  
> wrap my mind around the concept.  But you've made it much clearer  
> for me.  I still have a few follow-up questions...
>
> 1a) Forget the hypothetical company now.  Let's say 6 outside lines  
> were deemed sufficient, and there were 12 employee (i.e. inside  
> lines).  Could I have the same Digium T1 card to service out and  
> inside the company?

Yes, you could, but you will have to compare the costs of a  
fractional PRI or T1 with the costs of 6 regular copper POTS lines  
and the equipment needed to interface them with Asterisk. POTS lines  
might be cheaper, but you will need:

1.) 2 Digium TDM400p cards with FXO modules. These cards seem to be  
finicky, especially more than one, so you might want to stay away.
2.) Multi-port FXO gateway. VOIPSupply might be able to point you to  
some decent models
3.) T1 Card and a Channel bank with FXO Modules. You could even buy a  
channel bank that has 12+ FXS modules for the analog extensions and 6 
+ FXO ports for the incoming lines.

> 1b) I'm fairly certain of this, but anything going outside, I could  
> use the same T1 for receiving calls as for sending them, right?  
> (not with the same channel at the same time, obviously, but I could  
> use 2 lines incoming and 4 outgoing, or 3 incoming and 3 outgoing,  
> depending on the current situation, without reconfigurin the PBX?)

Yes. As mentioned by someone else, use the group functionality of  
Zaptel to let Asterisk select the next available channel

> 2) When you say a PRI is necessary for a Caller-ID name (as opposed  
> to just number), I've looked around and I understand a PRI uses a  
> T1 tunnel (24 channels) but a bit more expensive.  Is this a fact,  
> or is it something completely separate that I couldn't use with  
> Asterisk? Or am I completely out in left field?

A PRI uses a T1 loop, but you can only send voice or data using 23  
channels because the 24th channel is the D channel and is used for  
signalling. Our PRI was actually cheaper than what we were paying for  
our T1, but that might simply be due to the volume we sent over the  
line. Check with your provider.

[snip]

>> Yes, but you could use a Sangoma card, too.
>
> Will definitely take a look and compare.  Any pros and cons I  
> should know that isn't obvious from their documentation?

Well, Digium's latest firmware release seems to have made major  
improvements to their cards. However, the Sangomas are great cards as  
well, but they do require an additional driver, whereas Digium cards  
work without anything other than Zaptel. Digium's may do this as  
well, but I know that the Sangomas are capable of handling the D- 
channel signalling of a PRI directly on the card so that Zaptel  
doesn't have to do that.

>>> - 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?
>>>
>> 3.) Analog phones connected to a Channel bank, connected to a T1  
>> card.
>
> Thanks.  I already knew about SIP and IAX, since I'm more of a  
> computer geek than a telecom one that part means more to me :-)  
> Channel bank is what I meant.

Keep in mind that you will not need a channel bank if you are using  
SIP or IAX.

>> For something like this as your first serious production install, you
>> might want to consider hiring a consultant.
>
> I'll certainly consider that when (I should say if) a real project  
> does require me to do so.

Give me a call at that time, then!

> Thanks alot Tom, it makes me feel more secure in considering  
> Asterisk for jobs like this when there are helpful people like you  
> around.

It's who I am; it's what I do!

Tom

------------------------------------
Tom Rymes
Cascade Link Systems
www.cascadelinksystems.com
(603) 375-1414