What is a PRI Line, what are the advantages and limitations of PRI circuits
This article explains what a PRI line is, what are the benefits of having PRI lines for the telephony requirements of an organization, and the dis-advantages of a PRI line.
What is a PRI line?
- There is only one line physically terminating on the customer PBX but still a PRI line can receive/send 30 calls simultaneously! A PRI line is end to end digital circuit.
- A PRI (Primary Rate Interface) line is a form of ISDN (Integrated Services Digital Network) line which is a telecommunication standard that enables traditional phone lines to carry voice, data and video traffic, among others.
- A PRI circuit consists of two pairs of copper lines terminating on a modem from a service provider premises to the customer premises. It uses multiplexing/de-multiplexing techniques to carry more than one channel in a single circuit. There are two common forms of PRI lines – E1 (which carry 30 channels in the two pairs of copper lines, common in Europe, India) and T1 (which carry 23/24 channels in the two pairs of copper lines, common in United States).
- Each channel in a PRI line provides 64 Kbps for data transmission.
- A PRI line can connect to both Analog/Mixed EPABX systems and also the newer IP PBX systems. A PRI Card / Interface might be required to terminate the PRI circuit on the PBX.
- A PRI line can also be used to connect two PBX systems thereby providing 30 channels between them for interoperability.
Advantages of PRI Lines:
If thirty separate analog trunks are taken instead of one PRI line,
- The cost of terminating all the thirty analog trunk lines becomes higher than terminating one PRI line.
- There would be thirty rentals to be paid instead of one consolidated lower rental for a PRI line.
- Some analog trunks might be used more (uneven distribution of calls) and some lines may not have even crossed the free calls limit.
- Terminating 30 analog trunks in a PBX also requires more free slots/cards than the one slot usually occupied by one or even two PRI trunk cards.
- Direct Inward Dialing: For each PRI line, the service provider would provide more around 100-500 numbers which can be used by outsiders to call the extension directly, instead of having to go through the PBX Auto-attendant.
- Caller ID: Since all the extensions have their own number, this unique number will be displayed in the phones that they are calling to. Some call centre applications are based on the unique caller ID number for differentiation of services.
- It is possible to offer both voice and data in the PRI line. Some service providers have dynamic offerings where data is transmitted in all the channels that are free (not occupied by voice) at that given point of time.
- Call hunting (Where the call lands in any channel that is free, instead of the called number specifically – For example, if there is one board number but a number of people are calling in at the same time and still a channel is allocated to them .With analog lines, if one number is busy, they need to call in another number manually) is possible by default with a PRI connection, but for the analog trunks this facility needs to be extended by the service provider and enabled on the PBX, involving additional cost at times.
- PRI lines can be used for voice connectivity, data connectivity, video conferencing, faxing, and all the above can be done simultaneously too (on different channels).
- PRI lines are end-to-end digital lines and hence the clarity is much better than analog trunk lines.
- Since they are digital lines, PRI lines are more reliable and trouble shooting is also easier with them. They are mostly on a fiber core ring and hence there is some redundancy.
- It is harder to tap into digital lines and listen to the conversations.
- There are flexible billing options available with most of the PRI service providers. The billing can be centralized or distributed (department wise, etc).
- PRI lines take lesser time to establish calls then analog trunk lines.
- Some service providers offer flexible plans where instead of the full 30 channels, they provide and charge for only 20 channels etc. This makes PRI lines more economical for smaller companies.
Dis-advantages of PRI lines:
- A PRI line is economical only if the minimum rental charged by the service provider for a PRI line is more than the average value of calls with analog trunk lines every month in an organization. Otherwise, the usage may not even cross the free call value provided by the service provider for a PRI line.
- A PRI line is not so economical for long distance/ international calling. An ITSP or SIP trunk service provider who takes the calls over the internet might charge much lesser for international long distance calls.
- Inter branch communication between the branches is not free of cost with PRI lines (Some PRI service providers provide this facility, but all your branches may need to have PRI lines from the same service provider and there also might be a minimum revenue commitment for the same). With VOIP systems, inter-branch communication can be done over internet/ leased lines hence reducing the cost drastically.
- The cost of a single PRI card to connect to your EPABX/ IP PBX is still very high. Most of these cards are proprietary, meaning you can buy them only from your EPABX vendor.
Related Article: Difference between Analog Trunk Lines, PRI/E1/T1 Lines & GSM Gateway.
excITingIP.com
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good site
Pretty useful site for those who wish to boom in IT sector.
Well it is just a basic info….one can’t boom with this.
thank you
had good information
Tell me about the structure of PRI Line with drawing of equipment and connectors.
How it works ?
All the knowledge of PRI Line..
PRI lines mainly use in call center.
a single PRI line contain a 30 multiplexed channel.each channel in the provide 64 kpbs data trasmission.
physically connected in the only one line but still that managed all data trasmission.
But the end device in this mode of communication should be a VoIP enabled device……or can we use a GSM/CDMA device also….???
can some one help me out on this…???
The end device on this mode could be anything – analog. IP phones, etc as long as the PBX supports them. The PRI Line terminates to the PBX from the service provider and hence from the PBX, there could be any device. I am not sure how you could connect GSM/ CDMA device to a PBX, but a Wi-Fi enabled IP handset could be connected…
Yes a GSM or CDma device can be used if u connect your pbx system to MSC ( through ISUP ) . See PRI to SS7 gateways which makes
thanks,
its simply the best article about pri lines
While ISDN is a solid reliable technology it is in a loosing battle with VoIP, especially in green installations. Not only does VoIP offer savings in line rental and call cost it is also more flexible and doesn’t have the set up costs or tie ins of a fixed line contract.
However all is not lost. It can be worthwhile keeping hold of your ISDN lines if your thinking of moving to VoIP as part of a contingency plan. After all loosing your internet connection can cost you a lot of business and can be enough to justify keeping the minimum channel contract.
Can I use this for voice termination? where exactly can I purchase PRI line?
Yes you can use for voice. PRI is similar to analog FXO trunk lines, but instead of a single trunk line, PRI has 30 trunks bundled in a single line. Which means, you can make 30 incoming / outgoing calls at the same time (using 30 phones/ PBX).
Any telephony service provider (public telephone exchange) can provide PRI lines. Sometimes it is available even with ISP – Internet Service Provider in some areas.
Is the quality of PRI line from ISP of grey, standard or white route?
what is the difference using a PRI line with interconnecting with a direct route provider that offers its services with over IP to IP interconnection like IDT and Verizon
??
I am not very sure about the answer for this question – maybe you can ask those service providers….
pls tell me the convenient option for STD/ISD call With Pri? what will be the avg call charges using pri line ?is it economical for longer distance calling?
Per Call Charges for PRI lines are generally the same as normal lines… Instead of One line coming to your premises, 30 lines come & hence 30 callers can make incoming and outgoing calls using a single PRI line. There is a monthly rental, depending on your plan which gives a certain amount of free calls. So, go for PRI lines if there are a lot of telephone users in your company & you are confident of crossing the minimum number of free calls offered by your PRI plan. PRI lines are not advisable for individual (residential customers).
Thanks, i got the exact information which i required.
hi,
could u pls xplain the difference between PRI line and GSM gateway …
and which one is better??
I have written a separate article on that topic – https://excitingip.com/2111/telecom-trunk-lines-difference-between-analog-line-prie1t1-digital-line-gsm-gateway/
Thanks..That was very useful indeed..
Can any body will explain me the use of PRI line for Video Conferencing,the h/w requirement & the connectivity reliability for Video Conferencing.
A Video Conferencing system first needs to support PRI Lines, then you need to buy a PRI Module from the Video Conferencing manufacturer and plug your PRI line there to get 30 Channels. A Video session requires minimum 128 Kbps – So, with a PRI Line, you can do 15 simultaneous video conferencing sessions at 128 Kbps (but most of the VC systems do not support so many multi conferences), or four video conferences with different sites with a higher bandwidth for each site (like 512 Kbps).
But why do you need PRI lines at all? People either go for 3(or)4 x ISDN lines per video conferencing system (or) go for a pure IP installation with Internet Leased Lines if they need higher bandwidth/ do multiple conferences.
For existing VC users with ISDN I am not sure if PRI is a part of that. Some government sites will not move to IP because of security risks. Are ISDN lines part of that T1 that’s coming into the site? I always thought ISDN, especially for video tended to be 3 or 4 separate lines.
RE: ISDN is different from PRI/ T1. A Video Conference system might require ISDN BRI Module for connecting to individual ISDN lines (2 channels of 64 Kbps each) but requires a separate PRI module to connect with PRI/ E1/ T1 line (30 channels of 64 Kbps each).
good information
Excellent article, provide overall view of PRI
Thank you for very informative info!! good job.
can we use for voip termination,is it need any extra switches for termination apart frm pri
apART FROM PRI WHAT ALL NEEDED FOR VOIP TERMINATION,IS IT LEGAL IN INDIA
VOIP is different from PRI. PRI lines are used to call normal telephone numbers (cell phone and landline) to any state in India.
But VOIP is restricted in India. You can call your own other branches within your company using VOIP but VOIP cannot be used to call general public numbers within India.
However, it is legal to call phone numbers overseas using VOIP service. But that is provided by ITSP (Internet Telephony Service Providers) through SIP Trunks over Internet. But this is different from the dedicated PRI line you get from a public telephone exchange.
Hi kindly suggist me for PRI and BRI lines
Hi,
So as I understand, a single PRI line will allow me to make 30 calls simultaneously. Does that mean that I will have 30 different phone numbers on 1 PRI line? Plz reply ASAP.
Hi, thanks for the reply. A final question – Does the PRI line come with a contract attached to it? Most of the PRI line providers generally offer a complimentary PBX system – is there a minimum usage period associated with it?
PRI Lines give you a facility called DID – Direct Inward Dialing, if your PBX supports it. So, if your board number is 2533 1000, you can have numbers associated with individual employees as in 2533 1001, 25331002, etc. If someone calls on the board number, your receptionist / automated message picks up the call. But if someones calls on individual DID numbers, it will go to those extensions (employees) directly. PRI line providers generally provide 30 -50 numbers per line, and some of them can provide more if you want additional DID numbers.
On the other hand, if you want to have only one number – 25331000 but still want that number to take 30 lines (30 simultaneous calls), you can still use a PRI line and have a single number. In this case, all the calls go through the receptionist/ automated message of the PBX – its mandatory. But 30 people will be able to simultaneously call in or call out from that number.
hi, i need 42 telephone numbers from my service provider. how many e1 lines i require?
Do you need 42 telephone numbers or 42 lines for making as many concurrent calls? If it is only 42 numbers, then one E1 line (23 channels) will be sufficient.
Each E1 line gives 23 channels and around 50 – 100 numbers. But that may vary depending on your telecom service provider/ location. Please check with them.
But if you want additional channels, along with the telephone numbers you have to take one more E1 line.
is it possible to connect to pri line to analog epabx ?
Its possible to connect PRI lines with Analog PBX but your PBX should support the capability & you need an additional PRI Card which can be bought from your PBX vendor, if the PBX supports it.
halo…may i know what is CO line? is that similar to the telephone line in our house?
Yes, CO line is the same as the telephone line we get in our house. One can use it to make one outgoing call/ receive an incoming call (per line).
HI
how r u i have 1000 linz plz guide for me what can i do or i cnt handle these linz u have a any sulution
Hey, so I am trying to search up what I will need to create a long distance telephone company. Correct me if I am wrong anywhere:
From what I understand the first thing I need is to set up a PBX. From what i’ve read is that a PBX can be set up using Asterisk for linux.
Then I would need a PRI line into the PBX from a provider. This is basically the “internet” connection.
Then I would have to set up the exact same thing on the other end. Lets say somewhere in Europe.
So people would call a DID number (comes with the PRI line) which would then ask the customer to enter the number they want to call and then over a voip system and the second PRI line would establish contact to the homephone in the that country?
There are two common forms of PRI lines – E1 (which carry 30 channels in the two pairs of copper lines, common in Europe, India) and T1 (which carry 23/24 channels in the two pairs of copper lines, common in United States).
So, if I am using the T1 then I can only make 23 phone calls simultaneously.
Thank you in advance.
Yes, you are right.
we want to link two branch together through E1 PRI card through the internet, i know is possible due to my knownedge on it.kindly give details and the diagram ds is urgent matter
thanks you.
Lawal
It is possible.
Do you have the PBX and PRI cards setup already in your offices ?
dear all ,
can some one please tell me what other protocols are used for call control signalling apart from q.931 are there any other protocols used for PRI
Good website and will get good knowledge while going through the comments down here.. ThanQ !!!
OK, if you are setting up a system for a small office say 12 people and you want local, LD, internet, fax, data transmission. Would you use a PRI/T1, IP set up with access points and routers or something else. Also what do you call the handsets or phones and each line. This is very confusing because each estimate we get results in differing terms from suppliers. I am being told I need a T1, pbx,etc.
If you live in the US, why not look at SIP Trunks / IP PBX / IP Phones? This way, you can route all your voice calls over the Internet quite economically (especially for long distance calls) and there is only one network to manage (IP Data network).
More details on SIP Trunks – https://excitingip.com/2393/telephone-trunk-lines-what-is-a-sip-trunk/
Or you can order for ISDN/T1/Analog trunks as per your current and future requirements and set it up to run with analog phones/epabx.
Both are fine, and have their own advantages and disadvantages. If you are starting out now, maybe you can consider the former. If you already have all the analog phones in place, you might want to consider the latter. Still, its your choice.
Exxcellent article… thanks for sharing..
How will the customer get calling features? I mean voice mail,and other features that are available on analog lines and what extra calling features has a PRI line that analog lines do not have?
I think PRI lines support all the calling features supported by analog lines. Of course, voice mail/ caller ID etc needs to be supported by the telephone devices/ PBX used at the customer end. Additionally, they support some monitoring features which enables the telephone company to find out if the line is down and they help in quick diagnostics. Other advantages are listed in the article.
does this means All calling features such as voice mail, call transfer, call waiting, conference calling etc come automatically from the PRI line from the provider or the CPE needs to provide them? OR are these features residing in the PRI card? Can you please clarify..thanks a lot for your amzing insight.
I think these features are provided by the public switch equipment (at the service provider premises) and they need to be supported by the CPE – PBX at the customer premises. The PRI lines just support these features to be transmitted over them. I am not very sure about the role of PRI cards and if they need to support these features too.
I wish to use a single E1 to deliver voice calls through PBX and also do Video conferencing. I will like to know if this is possible. Note that i will deliver this E1 via microwave, i will also like to know if i should use TDM microwave or hybrid microwave link.
It is possible to use a single E1/PRI line to make calls and do video conferencing. You could talk to your PBX supplier to find out how to do this/see if your PBX supports this.
I am not sure about delivering E1 via microwave. Are you not able to pull a cable between the two premises?
Pulling a cable between the 2 locations is not possible. we can comfortably establish the link between the two premises using microwave link. if i drop the E1, which equipemts do i need to pass the E1 to make it usable for the voice calls (not voip) and video conferencing.
You’ll need a E1/PRI card on the switch but I am not sure if something else is required to support Video Conferencing.
If it’s only voice, the E1/PRI card on the PBX should be sufficient, but I am not sure what kind of output is provided by the microwave link. I think you should talk to your PBX vendor/supplier on this point.
You can get connection on RF through UBR or LBR , LBR is much better but a bit costlier that UBR and more reliable. output could be ethernet, but they can provide E1 using card or convertor. performance is all right depending on reception of signal.
hi, im starting a small call center, i have got the ISDN PRI line from BSNL. However they have stopped providing the supporting MODEM for the same. Can you suggest me some PRI Modem providers which will exactly fit my requirements?
I am having a pri connection. The modem which has been given by service provider is very old. I would like to know which are the most fastest modem which can be used for pri connection for dialling faster
this is a basic information which is very useful for that vendors who installing pri circuit .
can u please explain me why IP is so important and how VoIP works
Looking forward to your reply….
Have a look at this link – http://www.excitingip.net/35/an-introduction-to-voice-over-ip-voip-ip-telephony/
Cna u give me a full understanding of PRI?
good and useful site..
Hi,
You may also check this video on what PRI is. It is based on Ozeki Phone System XE and it fairly explains PRI and VoIP:
ozekiphone.com/download-333.html
BR
This is really valuable information for me…thanks a lot 🙂
What is CRC error in PRI lines .when we have to disabled CRC
Thanks to the author. This is a really clear article about a topic that can be somewhat dense to those outside the domain.
Hi,
I have an Idea , which is intended for a social cause.
Its called LEBTOP (Learn English By Talking On Phone).
Please visit http://www.lebtop.blogspot.in for more details.
I am looking for a telecom solution wherein , i want to connect callers to other callers.
If my number say 1800 xxx xxxx gets 100 calls at a time, i wish to connect incoming calls to other callers, thus I want to make 50 pairs of connections.
I do not know much about the telecom know-how, but some one suggested I use 4 PRI’s (to handle 120 simultaneous calls) but said that cost would be very high.
Your article is very well written and I assume you are an expert in this field.
Please go through our idea and help us realize it.
The idea depends on connecting callers to one another based on certain rules. Help us find a solution.
Regards
Nikhil Kukarni
please give me all details
Project LEBTOP
In short:
We wish to have a Toll-free number. When users call it , they will get 2 options-
Press 1 to Learn
Or Press 2 to Teach.
Challenge is to design a system which connects an incoming caller who has Pressed “1” to another caller who has Pressed “2”, so as to form a Student-Teacher Pair.
Thus we wish to connect two “Callers” through our Lebtop toll free number.
The solution that 1st came to my mind is .. Its as simple as , two friends calling my number and I merging their calls. This serves the purpose for 1 pair, but i guessed it can be done for 100’s of calls too, using modern Technology. But i’m struggling to find an answer to this problem.
Regards
Nikhil.
What if all 30 channels of my PRI used and I received incoming calls around 100 calls at any time.
If all the 30 channels of the PRI line are already occupied, any more callers will get ‘busy’ tone or can be made to wait (through the PBX). Additional callers will not be able to connect unless (at least) one channel becomes free.
most useful information.
What is Ip Phone?
A phone that connects to the computer network rather than a telephone network.
hi i am using single PRI and i have configured it as ACD (Directly land the call to CSR)but i want to do some change like :-
1. Suppose my PRI no is 810814001 ok and when the customer dial my this pri no then call should route via ACD. right now this function only working.
2. can i add one more Sub-number on same working PRI, is it possiable. bcoz i have divide my call centre in two parts A. ACD B. IVRS so my question is that can we use more then two different no on the single PRI line. if i got more then two sub number from my PRI service provider??? is it possiable ???
Every PRI that I’ve installed has only had 23 “voice” channels and 1 “d-channel”…. Don’t know where 30 came from…
T1, the dominant PRI standard in US has only 23 channels. But E1, which is the dominant PRI standard in many other countries comes with 30 channels.
Hi everybody
Can anyone pls give me the solution.
I have have a placement consultancy in delhi , currently we make calls through mobile phone, which is a time consuming process, infact my data base is not secure , bcz we maintain data base on execl sheets ,
So can anyone tell how can i make calls
1. i want predictive dailer.
2. with crm
3. any open source
4. currently need solution for 4 seats.
call me kamal 9873661346
chat2kamal@yahoo.com