said by raytaylor:
I imagine that with copper telephone plant, a subscriber's telephone line can be patched into multiple different trunk cables as it goes back to the telephone exchange.
Most commonly for copper there are two primary cables, one from the CO to the cross-connection box (X-Box or B-Box) which is referred to as the facility 1 (F1) and another cable from the crossbox to the serving terminal and from there its dropped to the customer, this cable is known as the facility 2 (F2).
Lets say a technician is dispatched to install service to a customer at 1010 main street from a terminal behind the customers business, connected through a crossbox behind a building at 400 Main Street, the technicians assignments might look like this.
BF1 CA 2 PAIR 1247 BP 247
AF2 R400MAINS PAIR 35 R1010MAINS BP 10
This advises the technician he is installing 555-1212, utilizing buried F1 cable 2 pair 1247, which will appear in the crossbox on binding post 247, from there he will place a cross jumper (PXJ) to a aerial F2 cable identified by the crossbox address on pair 35 which will appear within a terminal located to the rear of 1010 main street on binding post 10.