PRI and Traditional Voice Services


Primary Rate Interface or PRI is an ISDN (Integrated Services Digital Network) term used internationally to refer to what is essentially an ISDN version of a T-1 trunk.

In the Integrated Services Digital Network or ISDN, there are two levels of service: the Basic Rate Interface or BRI, intended for the home and small enterprise, and the Primary Rate Interface (PRI), for larger users.  Both rates include a number of B-channels and a D-channel. Each B-Channel carries data, voice, and other services.  The D-Channel is used for control and signaling information.

The Basic Rate Interface consists of two 64 Kbps B-channels and one 16 Kbps D-channel.   Basic Rate Interface user can have up to 128 Kbps service. The Primary Rate Interface consists of 23 B-channels and one 64 Kpbs D-channel using a T-1 line or 30 B-channels and 1 D-channel using an E1 line. Thus, a Primary Rate Interface user on a T-1 line can have up to 1.544 Mbps service or up to 2.048 Mbps service on an E1 line.  PRI uses the Q.931 protocol over the D-channel. The Primary Rate user is hooked up directly to the telephone company central office.

EarthLink Business SIP Trunking and PRI










Traditional Voice Services

Along with PRI, Caleidoscope Solutions offers a variety of traditional analog Voice Service products from numerous providers.   Analog Lines are often used for traditional residential, copper phone lines.  They are used with Key telephone equipment systems and are still highly recommended for use with alarms, fax and credit card machines.

Traditional analog voice services are connected via a 66 Block or 110 Block to the carrier provider or connected via an IAD (Integrated Access Device).   Services associated with traditional voice products can include

  • Local
  • Long Distance
  • Toll Free
  • Conferencing Services

EarthLink Business Conferencing Solutions

As an experienced broker of telecommunications solutions, Caleidoscope offers traditional analog voice services delivered by  BCN Telecom and New Horizons Telecom.