Centennial offers an Integrated Services Digital Network, (ISDN), which allows for sending voice, video, and data over digital telephone lines or normal telephone wires.
Primary Rate Interface (PRI) is Centennial’s most prevalent offering for Integrated Services Digital Network (ISDN). ISDN defines a set of standards for the digital transmission of voice, data and video signals over conventional transport media.   PRI is a dedicated connection between the customer's terminal equipment and the Centennial Central Office. The PRI supports up to 23 simultaneous voice calls, but may also be used for data applications, such as Internet access, thus reducing the total number of trunks needed.

Features and Components
PRI consists of 23 so-called B-channels, to carry voice or data traffic, and one D-channel, for signaling. The circuit must connect to an ISDN terminal adapter installed in the Customer Premises Equipment.

Benefits
ISDN affords many benefits to customers:  
• The ability to simultaneously support audio, video, and data services over a single pair of copper wires reduces infrastructure and maintenance cost for customers.

• Digital transmissions produce clearer and quieter voice telephone service and more reliable and accurate connectivity than analog technology.

• ISDN’s dynamic bandwidth allocation feature accommodates the bandwidth-intensive applications.

How Does It Work?
ISDN services presume Customer Premises Equipment capable of supporting the service via specific terminal adapters. Upon deployment voice and data traffic occupying contiguous bandwidth greater than 64 Kbps is switched via the Centennial TDM-network to any terminating point also equipped with ISDN capabilities. As indicated above, ISDN services are assigned specific BTN’s by Centennial.