A PRI-endpoint (PE) is a combination of DS0 B-channels on a line-side ISDN-PRI facility to which an extension is assigned.

A PE can support calls of lower bandwidth. In other words, a PE that has a width of six DS0 channels can handle a call of one channel of 64 Kbps, up to and including six channels totaling 384 Kbps. Also, a PE can support calls on nonadjacent channels. For example, an endpoint application that is connected to a PE that is defined as using B-channels 1 through 6 of an ISDN-PRI facility could use B-channels 1, 3, and 5 successfully to originate a call.

If the PE is administered to use flexible channel allocation, the algorithm for offering a call to the PE starts from the first DS0 that is administered to the PE. Since only one active call is permitted on a PE, contiguous B-channels are always selected unless one or more B-channels are not in service.

A PE remains in service unless all the B-channels are out of service. In other words, if B-channel 1 is out of service and the PE is five B-channels wide, the PE can still handle a wideband call of up to four B-channels wide. A PE can only be active on a single call at any given time. That is, the PE is considered to be idle, active or busy, or out of service.

One facility can support multiple separate and distinct PEs within a single facility. Non-overlapping contiguous sets of B-channel DS0s are associated with each PE.