[Asterisk-Users] Provisioning CO lines

[Steven Critchfield]

On Thu, 2003-08-21 at 10:20, Mike Ciholas wrote:
> Hi all,
> 
> This is a NEWBIE question, so all you experienced types that are 
> tired of stupid questions can move on...

Ah, but you followed all the right things to do, no HTML email, started
a new thread,  and you didn't demand someone solve your problem. You
asked for education in a polite manner. For this I hope many people
answer your questions.

> I've pretty much given up trying to do my entire phone system 
> over IP (including local service), so I have to select and 
> provision my local CO lines.  I need about 10-12 lines which can 
> be POTS lines, of course.  But, I thought, why not get something 
> digital and expandable like a DS1, PRI, T1 or whatever they call 
> it with 23 or 24 channels of 64 kbps voice.  It seems like it 
> would be simpler for me to deal with this (and better quality) 
> and it *should* be simpler for the phone company, too.

Your thinking is sound so far.

> However, while everyone can sell me POTS lines, when I ask about
> getting these in some sort of digital muxed interface, I seem to
> confuse the providers.  In one case, I was able to get something
> called "channelized T1" which cost a lot and did not actually
> include the "phone" service for any of the channels, that was
> additional.  So the cost to go from POTS lines to something
> digital was extreme, so much more than I can't understand why
> anyone would have T1 voice interfaces, yet all the PBXes have
> this and it seems commonly used.  I must be doing this "wrong".

It seems so funny how easy it is to confuse the Telcos about what you
want. They seem to be so used to dealing with at most a select few PBX
integrators who steer clients to them with all the appropriate
information filled out already.

> Okay, so I need help with:
> 
> 1. Understanding terminology so I can ask for the "right thing".

You may have a hard time getting PRI in so few channels, but PRI is
probably what you would want. You may also need to reference it as ISDN
PRI. DS1 is the same as a T1. Channelized T1 is usually RBS and is only
a 56k voice channel( 7bits, 1 bit is robbed for signaling). Channelized
T1 is basically analog service multiplexed onto a digital trunk. 

More for why PRI is probably a better option, if you have customers who
complain about how many rings it takes to answer the phone, PRI can
signal your PBX about the call before a ring is ever generated. Your PBX
can even answer the line with out a ring being generated. I never knew
doctors could be affected by as little as 1 ring difference in pickup
time, but they let me know when I went behind our asterisk box that the
reduction from 2 rings to 1 ring was great.   

> 2. Advice on when it is reasonable to go POTS versus something 
> else and what that something else is.

Basically your choices are POTS or T1. It is reasonable to go POTS for 5
or fewer lines as the cost of transport on a T1 is higher than the cost
of the 5 lines. Above 5 lines and hardware starts becoming a problem. At
around 10-12 lines the cost and scalability should start to swing in
favor of T1 and will increasingly do so as you add lines. Our PRI costs
us about $30 per channel of voice, before we get into some site specific
fees, but in this cost we get callerid and 20 DIDs and it seems the
ability to send whatever callerid we choose(found this out using the
iaxclient software for windows, saw a 700123456 number on a cell phone).

> 3. Feedback on what others are doing with 10-12 lines in the US 
> that may want to expand to ~20 lines.

PRI sounds like your best bet if you can get it below 23 channels, as it
wouldn't take much for them to just turn up a new channel for use. 

> 4. Interfacing so many POTS lines to Asterisk.  I guess that
> means an FXO channel bank to T1 card?  Kind of stupid to go
> digital/analog/digital in the last 100 feet.

Yep, not to mention that even used FXO channel banks cost almost as much
as they where new.

-- 
Steven Critchfield  <critch at basesys.com>