You can download a link below to a PDF document which goes through the process of tracing the LCR programming for the NEC 2000IPS. When we refer to "LCR" in the NEC PBX programming, we're not just talking about ways to make cheaper calls. It does indeed cause route preference choices depending on the location, extension, tenancy and more - but also is responsible for barring, time scheduling, volume control and so much more.

This flowchart takes it down to the very basics and should be noted that it's based on traditional UK programming of the NEC IPS. Therefore it may bear no resemblance to your standard programming, but if you study closely, you'll soon figure out what does what and where.