Covers the technical data and performance for interconnecting and interfacing the various functional groups shown in Figure 1. Compliance with this standard is intended to ensure compatibility at the interface points 1a and 1b (Figure 1) and should not be construed as a constraint on the internal operation of the Terminal Equipment (TE), or Network Terminations (NT). Consistency is the intention of the provisions in this Standard with applicable requirements concerning environmental and safety conditions. Equipment for customer installation shall be subject to applicable safety requirements, and the rules of the Federal Communications Commisions.