[asterisk-users] Learn some terminalogy before mounting this task.

Tue Apr 10 21:13:07 MST 2007

Alex,
First may I offer thanks for your comment and reply. Most I understood and all I appreciate.
To clarify the existence of the Channel bank at our current premise:
In past years the Data and Voice WAS on the same T1. The 24 channels were used(The T1 was full) and the channel bank separated (At that time marketed as->) DPL (Digital Private Line) circuits to our two branch offices.
That has long been changed. We now have a separate/new T1 for data and the original T1/channel bank which is in fact only for voice. When I talk with our CLEC (USLEC) I should now expect them to tell me there are only 7 channels provisioned on the Voice T1. (If I understand your comments)

----

Also,
Sounds as though I should compare pricing to a PRI ISDN circuit and inquire about our current Voice T1's signaling (I wonder if this is in reference to CLOCKING of a TDM circuit?)
We will need a few Analog lines for various IT Dpt. issues therefore a Zapata T1 card for the Asterisk server is out. Also, an earlier reference to 'A port' comes for my reading about the TDM400 cards. That material states the card has 4 'ports' configurable to FXO or FXS type 'ports'. If I understand your comments, 1 Channel of a T1 OR PRI equals 1 port on an TDM400 card or OpenSwitch12 for that matter.

Lastly, I have seen recommendations to only install ONE card within an Asterisk server for stability and performance reasons. Are we past that need with todays current baseline server products?

Again, Thank you and anyone who replies to this dialog. It is very appreciated in helping raise confidence with this project.
--------------------------

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com on behalf of Alex Balashov
Sent: Tue 4/10/2007 9:41 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] Learn some terminalogy before mounting this task.

Hi James,

   Admittedly, the terminological and conceptual barrier may present some 
impediments to the completeness and specificity of answers, so we might 
have to work at this a bit, but let's see how we can help:

On Tue, 10 Apr 2007, James R. Stevens said something to this effect:

> We have a T1 coming into the building(FYI-Our Voice and Data are on
> separate T's) terminating at the Smart Jack.

   Are you implying that there are two T1 circuits -- one voice, and one 
data?  Or do you mean that the T1 is channelised and some of the channels 
are used for voice and some for data?  That's kind of what it sounds like. 
Sounds like you can do 7 calls on voice channels and the rest are 
provisioned as a clear-channel data pipe.

   That would mean that you have some equipment for breaking them out on 
your premises.  The channel bank would break out the voice lines as FXO 
analogue lines (if you set it to) and those probably feed into your PBX. 
The rest of the channels used for data would probably be signaled out on
another T1 interface, but with some subrate DS0 channels missing.  That's 
ust a guess.

   But what you say below suggests that my theory is wrong, so perhaps it is 
the case that you have separate voice and data T1s after all, even though 
you refer to it in the singular.

   Do be aware that under no circumstances does anyone generally refer to a 
T1 as a "T."  :)

> I can tell you our current phone system can handle 7 phone calls at a
> time:
>
>   Does this mean the T only has 7 channels provisioned out of the 24
> possible?

   This is possible.  Do you happen to know what kind of signaling is used 
on it?  Is it an ISDN PRI, or an E&M trunk?

>  Does a channel (In terms of the T1) = a port?

   A port on what?  The channel bank?

   Channel banks generally do break the DS0s (subrate 64 kbps channels, of 
which there are 24 on a T1) out, but some more sophisticated ones have the 
capability to do other things as well.

   If so, the answer is yes.

>  How many phone calls can one TDM400 support concurrently? (four ??)

   If it has four FXO ports and four FXO modules, yes.  They come in 
different combinations.  Some come with 2 FXO (outside POTS lines to CO) 
and 2 FXS (plain analogue POTS handsets) ports, etc.

>  Would I be better off getting a Zapata T1 card and forgetting the
> Channel bank all together(Use the digital signal)?

   You could do that.  Personally, the easiest approach I would say would be 
to order a PRI.  They've probably considerably gone down in prices, too, 
especially if you go shopping with some friendly CLECs.  The rule of thumb 
in the industry is that generally, once you pass the threshold of six or 
seven POTS lines, it becomes economical to just order an entire PRI, and 
once you do that, there usually aren't *very* considerable savings to be 
gained from turning down all but a few channels.  A PRI has 23 channels 
(bearer channels ("B channels")) and one signaling channel ("D channel"); 
it's a type of T1-based ISDN interface.

   So, you might potentially be able to get 23 in/outbound phone lines for 
roughly the same cost or a modest increase, which would increase your 
organisation's capacity to do things like conference calling and other 
things which tie up large amounts of outside lines.

   Do beware that if you go this route, PRIs can be ordered as "inward-only" 
(typically used for modem and termination-only telephony applications like
voicemail, IVR, conferencing, etc.) or bidirectionally.

> If we go with a Zapata T1 card for the Asterisk server would we be able
> to provision an analog phone line, for say a FAX machine from it?

   No, not if the card doesn't have FXS ports on it.  But you could get 
another Digium or Digiumlike card that does, even if it's just a 
single-port (like the hugely popular X100P, which is very inexpensive)
and pull that off.

   Let me know what else we can answer, or if I substantially misunderstood 
your question.

Good luck,

-- Alex

--
Alex Balashov <sasha at presidium.org>
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