PRI T1s

What Is a PRI T1 and How Could It Help My Business?

PRI stands for Primary Rate Interface.

A PRI T1 has 23 universal ISDN voice pathways that give you very intelligent voice channels for caller ID control on both incoming and outgoing caller ID.

Clients are capturing your caller ID numbers on their office phones, cell phones and home phones. With a PRI T1 we setup your system to output your main advertised number or numbers.

Without PRI T1s, plain business phone lines are usually used. Phone systems pick the last numbers in your roll over group and send out those odd caller ID numbers. With plain business lines there is no way to out pulse your main phone number all of the time because there is only one of them.

One PRI T1 can have a virtually unlimited number of phone lines assigned, called DID’s (Direct Inward Dial) because the 23 channels are all universal in and out channels.

You purchase phone numbers (DID’s)  for PRI T1s usually in blocks of 20 numbers for as little $.15 per number.

PRI’s require a PBX to function and provide tremendous functionality. For example,  businesses can provide each employee, department, or even handset, with their own direct phone number. This will allow you to set up a one call “does it all” line for your customers. This is a powerful and inexpensive way to stop missing calls. Missed calls many times turn into lost revenues.


ISDN PRI provides:

  • Guaranteed dynamic bandwidth over non-shared lines.
  • Ability to prioritize call demand for each type of traffic (DID, DOD, data and toll-free)
  • A wide range of features at one standard cost.

How PRI Works:

A more sophisticated T1 line configuration is called T1 PRI or Primary Rate Interface. This term comes from ISDN or Integrated Services Digital Network) technology. A PRI line is also channelized into individual telephone lines, but carries 23 simultaneous calls rather than 24. What happened to the other channel? It’s been assigned to be a data channel to serve the 23 bearer or voice channels. All the dialing information is passed through the data channel rather than as touch-tones over the voice channels. That helps make call set up and tear down faster. You’ll experience that as phone calls going through faster. On the receiving end, the data channel accepts Caller ID or ANI information. This can be fed to display units to show who’s calling, or fed to a CTI (Computer Telephone Integration) system so that customer information will pop up on an agent’s screen based on the number of the incoming call.

With ISDN PRI, you can:

  • Use your existing infrastructure to enable all digital, high-speed voice and data applications that increase productivity.
  • Dynamically allocate channels to adapt to changes in traffic patterns and increase trunking efficiency by up to 30%, reducing total trunks required.
  • Leverage advanced features to support call center applications, or to extend the life and value of an existing PBX system, while reducing call set-up and connection time by up to 90%.
  • Cost-effectively connect multiple locations with guaranteed, two-way bandwidth that can carry voice and data, all via the PSTN.
  • Transfer large volumes of data and enhanced voice over instantaneous connections with superior transmission quality and.
  • Implement a cost-effective, robust disaster recovery/back-up solution to protect mission critical traffic on a wide area network or traditional T-1.