In telecommunication, a primary rate interface (PRI) is an integrated services digitalnetwork (ISDN) interface standard (a) that is designated in North America as having a 23B+D channels, (b) in which all circuit-switched B channels operate at 64 kb/s, and (c) in which the D channel[?] also operates at 64 kb/s.
Note: The PRI combination of channels results in a digital signal 1[?] (T1) interface at the network boundary.
... there are two different solutions x, both of which are real. (Geometrically, this means that the parabola intersects the x-axis in two points.)
If the discriminant is ...