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Enjay Synapse works on the PRI line, whereas many people are still using PSTN lines, there is a huge difference in pricing, working & technology of both. There is always one question – PSTN v/s PRI.


On the Internet, you might find many many articles which explain the technicalities in detail, but this article will help you understand the whole technology from a layman’s point of view.


PRI connection seems to be costlier @ first glance, however, if we understand the benefits correctly – we will realize that we can save lots of money.


Note: this is not a comparison between Enjay Synapse Server and PSTN lines – Enjay Synapse Server has many other advantages – which will be covered in another article.


A more detailed version of this article will be shortly published on www.ens.net.in in the Enjay Synapse section.



  1. PSTN – Public Switched Telephone Network – which in other words is our normal phone Landlines which we get from BSNL / MTNL
  2. PRI -Primary Rate Interface – don’t go by the Jargon, in simple words, it’s a digital connection – which gives you 30 simultaneous telephone conversations.
  • Of course, PRI can be used for lots of other things – but to make things simple, we will stick to this definition.

Generally, people argue that they use 6 or 10 PSTN lines, hence, can’t afford PRI connection. Here are some points for their consideration.


Advantages of PRI :

  1. Crystal Clear – digital voice.
    1. Everything in PRI connection – all the equipment, cables, protocols – everything is digital – nothing is analog.
    2. As a result – you get a crystal clear voice – which is un-imaginable in the case of normal PSTN lines.
    3. Why? In the case of PSTN lines, there is a conversion from digital to analog @ more than 2 levels – when one call is established. – This conversion leads to lots of disturbances.
  2. Extremely fast call connection
    1. You will be surely surprised when you use the PRI for the first time, it’s amazingly fast
  3. Pooling of bill for all 30 lines
    1. If you have 10 PSTN lines, with the same or different calling plans – you will have to manually decide from which number to make calls.
    2. It may happen that for the first 3 numbers – you make lots of outward calls – and end up getting a huge bill.
    3. Whereas for other numbers – you don’t even use the free calls.
    4. Now, with PRI – this is automatically solved – all the calls from all the 30 lines are pooled together – when you are being billed.
  4. Automatic Call Distribution
    1. With these 30 lines, you get 100 numbers – which means they are your hunting lines – if one line is busy the call can land on the next line – your customer never gets a busy tone. – GREAT feature
  5. DID – Direct Inward Calling.
    1. You can publish various telephone numbers for different people/departments in your company.
    2. Example – 0260-6612900 is supposed to reach Enjay Sales Desk, 0260-6612950 will reach Support Desk directly.
    3. This feature is built-in into PRI technology, for normal PSTN lines, this is not available – it has to be done through an expensive EPBX box.
  6. DOD – Direct Outward Dialling
    1. Many times it happens that you receive a call from some company, and you are not able to pick up the call.
    2. Now when you call back – the call lands to the receptionist – she has no idea who made the call.
    3. This happens because a normal EPBX – makes outward calls thru any available telephone line.
    4. With PRI – this problem is solved – the call is always made outside using the user’s DID number – which means that the person being called – if calls back – the call will land exactly to the person who had originally called.
  7. Easily expandable
    1. PRI line is actually a 2 Mbps line, which utilizes 64 Kbps for each call. This is also called the E1 line – which has 32 channels of 64 Kbps – out of which 2 are for control and the rest 30 are used for communication.
    2. So, the number of PRI lines can be increased on very short notice.
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