newbie question on for the PBX world.

Also here are some resources: (Netwons dictionay is the bible for the PBX industry)

Some books to study:

Newtons Telecom Dictionary, by Harry Newton

Guide to T-1 Networking: How to Buy, Install & Use T-1 From Desktop to Ds-3
by William A. Flangan


Here is a list of links to keep you busy this weekend:

http://www.protocols.com/pbook/VoIP.htm
http://www.protocols.com/pbook/VoIPFamily.htm    basic overview of VoIP

http://www.cisco.com/warp/public/788/signalling/net_signal_control.html      basic telecom link

http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_tech_note09186a0080174804.shtml    debug sample

http://www.cisco.com/application/pdf/en/us/guest/products/ps5037/c2001/ccmigration_09186a008011bd39.pdf   all of IOS voice commands

MGCP rfc's below

http://www.faqs.org/rfcs/rfc2705.html
http://www.faqs.org/rfcs/rfc3525.html
http://www.faqs.org/rfcs/rfc3660.html
http://www.faqs.org/rfcs/rfc3661.html

SIP RFC's

http://www.ietf.org/rfc/rfc3261.txt
http://www.ietf.org/rfc/rfc3311.txt

What type of connection is normal supplied from the teleco for DID service.  I assume you cannot have them simply install regular POTS line jacks at your location and you have to have a T1 or something similar setup?  

Am I correct in understanding your comment as: If you purchase a DID block of numbers from the teleco for 555-1200 - 555-1300 you would logically have 100 numbers for your organization... but with only 10 circuits you can only have 10 Active, External conversations going on at any given time. ??

In regards to the block of numbers, you buy the numbers and then you but the circuits, so though you have a 100 numbers, you can only haqve 10 conversations if you only have 10 circuits. But you are not limited to this, you could have 50 circuits with a 100 numbers. Or 2 circuits for a 100 numbers.

The goal of DID service is to provide automatic call routing without the high cost of individual leased lines and physical equipment.

Also in the early days the circuits were only for inbound, but that has changed in many areas and the same circuits can be used for outbound dialing also, this is typically on a digital circuit, and referred as a DIOD (Direct Inward/Outward Dial)

I need to clarify here for one moment PRI is an arconym for ISDN wich has an A and B channel combited to 128k A T1/DS1 has 24 channels which all could be "partioned" for voice traffice like in our example above.  So if we had a T1 for this service it could have 24 voice paths because it has 24 channels?  Likewise an ISDN/PRI could have 2 voice paths because it has 2 channels?  or am I way off?

I have an idea what to expect if we orded DID service using a digital line... but if they use a specialized analog circuit to deliver service what can I expect the phone company to install for me.  Would they put in a large block of some type that I would have to wire to my FXO interfaces?  So if I had 10 voice paths delivered to me on this special analog circuit I could expect a punch down block with 10 connection points that would then need to be hardwird to my PBX?

Thanks :D

Analog DID service is connected to specialzed PBX cards for that purpose, if you connect a phone directly to it it can cause many types of problems. The analog DID circuit is a two wire circuit that is normally wired to the PBX making sure to reverse the polarity when doing so. From a wiring perspective, the analog DID and POTS circuits use the same wiring.

In regards to T1/PRI: This is something 90% of Data and Telecom people get mixed up, the book on Guide to T1 Networking is good to have.

T1 is really not a service at all, but over the years the term has ben misused but excepted as the actual service. T1 is the actual medium that digital services are delivered on. The simple definintion of the T1 is a 4 wire circuit that has a data thruput of 1.544 MB per second. The circuit uses repeaters/signal booster every 6,000 feet. The services that can run on the T1 are PRI and DS1.

DS1 (Digital signal 1) is 24 DS0 (DS0 is a 64K channel), DS1 is that what is normally reffrered to as the T1 service in regards to voice,
PRI is also a service that is comprised of 23 B channels and 1 Data channel for signaling. So DS1 deleivers 24 channels of voice, where as PRI delivers 23. There are variations of this, but this you can find out from the forementioned books.

The best way to look at T1 and the services, the T1 is the highway, DS1 aqnd PRI are the type of cars you are driving.

Ok I was way off then on my definitions.  BTW, I have ordered the T1 networking book that you recommended ;)  So in regards to ISDN, PRI has no dealings with this?  I thought that using a ISDN line could be used in the same was as a T1 online for smaller installs.  You are right about the confusion with the T1 term.  There are even some cable internet companies selling T1 service and use this term only represent the speed the speed that you would be receiving. Hmmm ;)

As for DID service if an analog circuit was the only delivery method in an area for the service (we have some remote sites in the sticks) how would that then be connected to an Asterick type of installation?  From what I understand Digitum or whatever does not make cards for this service and would require the use of the T1/E1 cards... so therefor would not be a possible solution.

ISDN has two flavors: BRI and PRI

BRI is 2B+1D
PRI is 23B+1D

In regards to the analog DID issue, you could use a Cisco router that supports analog DID, then have the router be a SIP gateway for the Asterisk pbx.

akant74,

Also Newtons Telecom Dictionary has all the defeinitnions you would ever want. Almost a thousand pages strong.

Hope all this has helped!

Kindest regards,

Joel_Sisko

akant74,

Hope all is well, do you need any more info?

Kindest regards,

Joel _Sisko

Joel_Sisko has earned this one .... well done indeed!   ....

Thanks rwotherspoon!