Difference Between ISDN BRI and PRI Interface (With Table)

Telecommunication has played a wider role in the development of this modern world. The invention of the radio paved a way for a gigantic field which made huge leaps and tremendous improvements in sending and receiving messages or data across the world. While it took days to communicate a message to a nearby city, it takes only a fraction of minute to send and receive messages to any part of the world at present. Broadband internet connection, together with VOIP and DSL is presently used everywhere in telecommunication.

Before internet and VOIP (Voice Over Internet Protocol), ISDN (Integrated Service Digital) was popular in telecommunication due to its transmission of video, data and voice simultaneously on a digital line over a telephone network. In fact, ISDN spearheaded the transformation of the analog telephone network to digital lines. The two main types of ISDN were BRI (Basic Rate Interface) and PRI (Primary Rate Interface). Though BRI and PRI belong to the same category, they differ in the service they provide to its users. While BRI provided a low-cost service, PRI remained as the main service due to its very high performance and reliability.

ISDN BRI vs PRI Interface

The difference between BRI and PRI is in the communication channel. PRI has twenty-three bearer channel and one data channel in the T-carrier transmission network. But BRI has only two bearer and one data channel in its network configuration. One should take a note that a single B channel can transmit data at a speed of 64 kbps (kilobytes per second).

This data could give an overall idea on how fast the communication would be in PRI network as it transmits data at a rate of 1.536 Mbps (Megabytes per second) which is twenty-three times faster than BRI.

Comparison Table Between ISDN BRI and PRI

Parameters of ComparisonBasic Rate InterfacePrimary Rate Interface
DefinitionIt is one of the two types of ISDN interface, primarily for small-scale and home usage.It is a telecommunication interface intended for medium and large business firms.
Number of Bearer ChannelTwo bearer channels.Twenty-three bearer channel in T-carrier and thirty bearer channels in E-carrier interface
Number of Data ChannelOne data channelOne data channel in both E-carrier and T-carrier.
Transmission SpeedA maximum speed of 128 kbps.Maximum transmission speed of 2.94 Mbps in dual PRI.
FeaturesLow-cost.Higher transmission speed with greater reliability.

What is BRI Interface?

Basic rate interface is the primary ISDN interface used in home and small-scale enterprise. It is the basic level of service in the ISDN network. BRI interface helped in receiving or sending data from multiple users at a time. It has two bearer (B) channel and one data (D) channel. Among the two B channel, one B channel is used for transmitting signal and another B channel is used for receiving the signal. Bearer channel helps in carrying voice and data. Data channel helps in carrying signal and control information.

B channel transmits the signal in a circuit-switch network whereas D channel transmits data with the help of packets. BRI uses a pair of single twisted wire for data transmission. A single B channel can transmit data at 64 kbps, So, it is clearly visible that BRI cannot transmit data not exceeding 128 kbps. The data channel can transmit data at a rate of 16 kbps. Despite being able to transmit data at a slower speed when compared to PRI, it was popular among household and small-scale firms due to its low cost.

BRI did not gain popularity among large enterprises due to its low speed and reliability. To be precise, BRI acts as a level for basic service. BRI was primarily meant for subscriber lines in telephone service.

What is PRI Interface?

PRI stands for primary rate interface. PRI was the main interface which was preferred for high-speed internet access during its introduction in the market. There are two types of BRI carrier. They are T- carrier and E-carrier. The T-carrier configuration has twenty-three bearer channel and one data channel. T-carrier configuration is generally used in America and Japan. While E-carrier boasts thirty bearer channel and one data channel. E-carrier configuration is used in Australia and the European region.

The main reason for its high-speed network connectivity is because of the communication channel it possessed. As the number of bearer channel increases, the transmission speed also increases. There are twenty-three bearer channels, meaning that the transmission speed will be at 1.536 Mbps approximately. This high speed was the reason behind large firms preferring PRI to BRI.  

Though PRI was efficient and reliable, people started searching for other alternatives due to the high cost. This resulted in the broadband network and voice over internet protocol (VOIP). Slowly ISDN (both PRI and BRI) network started losing its sheen due to high expenses when compared to its competitors. Nevertheless, the ISDN network is still used to transmit high-speed internet in absence of broadband connectivity.

Main Differences Between BRI and PRI Interface

  1. Primary rate interface is the preferred mode of communication for a high-speed network when compared to the basic rate interface.
  2. Basic rate interface was adopted in the household due to its low cost in service.
  3. Primary rate interface has higher reliability and performance in transmitting data when compared to the basic rate interface.
  4. Primary rate interface is adopted mainly by large companies whereas small-scale companies prefer basic rate interface system.
  5. The introduction of broadband harmed both primary and basic rate interface in which basic rate interface suffered a lot than the primary rate interface.
  6. The only advantage of a basic rate interface over primary rate interface is the cost difference which is not over-looked by people looking forward to high-speed network access.


Both BRI and PRI paved the way for digital transmission of signal and data which lead to multiple developments in the telecommunication field. Now, broadband and other network interface have occupied space which was in the hand of the ISDN network. While BRI has been phased out, PRI is still in use where broadband connectivity cannot be laid.


  1. https://link.springer.com/chapter/10.1007/978-3-642-60794-3_9
  2. https://ieeexplore.ieee.org/abstract/document/6770427