Primary rate interface (PRI) is a telephone service that allows multiple phone numbers to transverse a single, or multiple, T-1 or circuits. PRI provides a multiple number of channels based on the standards established by a country or geographic location. In North America, PRI’s consist of 23 voice channels and 1 data channel which communicates between the carrier and the customer equipment.
One of the main reasons a business will deploy a PRI is when is has a need for multiple telephone numbers but their usage does not warrant having an individual line for each number. PRI’s allow multiple numbers to come to a location without the high cost of carrying an individual line for each number.