PRI is Primary Rate Interface which is a standard that lies within the ISDN or Integrated Services Digital Network framework. PRI denotes a specification meant to carry voice and data transmissions. The ISDN also has something known as the BRI which is Basic Rate Interface. The PRI and BRI differ in their level of service. The PRI is characterized by:

  • Being based on either T1 or E1 lines which have 24 and 32 channels respectively,
  • Providing differing number of channels across a few countries
  • Typically consisting of 23 bearer channels (B) and one 64 Kbits per second channel (D).