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T1 PRI (Dedicated Voice)


An ISDN-PRI (Integrated Services Digital Network-Primary Rate Interface), typically referred to simply as a PRI, is a way of delivering faster, enhanced voice service over a T1 circuit. Generally used for medium to larger businesses with more modern phone systems, a PRI system has a total of 24 channels, with 1 ‘delta’ (D) channel carrying caller information and control signals while the other 23 ‘bearer’ (B) channels are used to transmit voice and data information through the lines.

A PRI system is flexible, feature-rich and cost-effective. Going beyond providing basic caller ID information, it can generate ‘screen pops’ — customer information and history that pops up on a computer screen prior to an incoming call being answered. Businesses, such as hotels and call center operations, most often opt for PRI service because of another important feature known as Direct Inward Dialing (DID), which gives the end user the ability to assign individual direct numbers to every employee in the company without having to pay a fixed cost per line (as is the case with analog phone service). What this means for the customer is they avoid being placed on hold since DIDs channel them directly to the appropriate person or department, and it also allows them to bypass general greeting instructions (e.g. press ‘1’ for sales, ‘2’ for company directory, etc.) that can sometimes be drawn out, redundant or confusing.

Unlike Dynamic or Integrated T1 offerings, a T1 PRI is considered a ‘true’ PRI because all 23 bearer channels are normally dedicated only to voice traffic. This ensures impeccable call quality since bandwidth isn’t fragmented between phone and internet usage, so there will never be an issue with voice degradation. This is especially important given the large call volumes that these companies experience throughout the day and, hence, the reliance placed on telephony service.