This standard covers the general parameters and characteristics associated with telephone loops from the subscriber signaling and analog voice frequency interface to the local Class 5 switch interface. It includes only those business and residential lines in the North American public switched network where no special performance requirements are involved. This standard provides common denominators for subscriber line performance, independent of facility types, construction processes or equipment, and circuit provisioning methods. This standard does not attempt to allocate impairments to the individual facilities and equipments that comprise the subscriber line. Such allocations are performed by the service providers to achieve the overall loop and telephone system performance.

The purpose of this standard is to describe quantitatively the performance characteristics of telephone loops and indicate current acceptable performance criteria.