This standard is one of a series that defines and describes service capabilities within the context of an integrated services digital network (ISDN). This service capability 5 be made available on a demand or subscription arrangement. The interaction of this service capability with other service capabilities defined in other American National Standards is also included. The purpose of this standard is to allow maximum compatibility among network-and user-owned telecommunications equipment's in order to increase the attractiveness and usefulness of ISDN-based capabilities. The multi-level precedence and preemption (MLPP) service provides prioritized call handling service. This service has two parts - precedence and preemption. Precedence involves assigning a priority level to a call. Preemption involves the seizing of resources, which are in use by a call of a lower precedence, by a higher level precedence call in the absence of idle resources. Formerly known as T1.619-1992(R2005).