asterisk users - Apr 2007 - Learn some terminalogy before mounting this task.

All,

I have done research on VoIP for some time now. I'm a Cisco certified
Network Engineer however Telecom is not my strongest suit. I've been a
part of this mailing list for sometime but my delusions of grandeur in
migrating our 25 year old phone system to a new platform have been on
the back burner, until now. I have found my company is moving to a new
location(building) and this provides perfect opportunity.

 

Long story short, I'm very Linux savvy having no problems compiling,
building, making etc.. However getting connected to the PSTN is puzzling
me. My vocabulary is lacking and I need to call our provider this week
and get some circuits moved. So, my confusion....

 

(Current Setup)

We have a T1 coming into the building(FYI-Our Voice and Data are on
separate T's) terminating at the Smart Jack. Then a cable from the T
card(SmartCard) to the channel bank. From the Channel bank lines are
punched down to the block. Then those ANALOG lines are fed into our Big
hunking PBX mounted on the wall and two (Looks to be Rj11) lines come
from it into our VM server.

 

Q&A..

 

We are going to leave the telecom hardware behind.. I want to replace it
all with an Asterisk or Tribox solution.

 

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?

 

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

 

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

 

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

 

  Or Have a channel bank installed and use an OpenSwitch12 solution
working with the analog signal?

 

 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?

 

(Further information)

Ultimately this is the FIRST of 3 offices that will be migrated. This
first office has 30 physical phones and currently no DID (Hoping to
change that as well) Once the second and third offices migrate(about the
same number of stations) we would connect the 3 Asterisk systems over
the WAN giving us free long distance between offices.  The toughest
challenge I foresee is getting overhead intercom/paging to work(We must
be able to hail our warehouse staff over head), also Music on Hold... If
I use Cisco 7940's (SIP) (Or the like) I'd like to integrate our phone
extensions for a 3 offices into the directory

Does this sound do-able?

 

 


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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@presidium.org>

On Tue, 10 Apr 2007, Alex Balashov said something to this effect:
> Personally, the easiest approach I would say would be to order a PRI.
   The reason I say that, by the way, is because most T1-based digital voice 
trunking is done using PRIs these days.  That doesn't mean you couldn't
get a
good old-fashioned E&M trunk -- which is what would typically be used on a 
classic "channelised T1" (which uses "channel-associated
signaling" (CAS)
rather than out-of-band PRI signaling on the non-bearing "D channel"),
sometimes at a considerable discount from the telco.

   The Zaptel-compatible T1 cards support that as well.  But PRI is a lot easier
to manage for a variety of reasons IMHO, and is generally preferred.

-- Alex

--
Alex Balashov <sasha@presidium.org>

James,

I'm sorry that I can't add anything but just wanted you to know that I
am watching this thread with great interest and suspect that many others will
too.

Thanks in advance for posting lots of details as you go thru the process.

Pierre

>>> abalashov@evaristesys.com 4/10/2007 10:41:36 PM >>>
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@presidium.org>
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