A technology that uses electric power transmission lines and inside wire for telecommunications transmission. The technology was invented in 1928 by AT&T Bell Telephone Laboratories, and has been used since that time by the electric power utilities in select internal low speed data communications applications. Some customer premises equipment (CPE), such as small key telephone systems and intercom systems, based on PLC technology has made use of embedded inside electrical wire to avoid the cost of special wiring. In Europe and most of the rest of the world, PLC standards allow for communications over the 240-volt power grid at frequencies from 30 kHz to 150 kHz. In the United States, the standards for the 120-volt grid allow the use of frequencies above 150 kHz, as well. Power utilities use the frequencies below 490 kHz for internal applications such as telemetry and monitoring and control of equipment at remote substations. In the 1990s, development began on broadband over power line (BPL), which since has been standardized. BPL includes Access BPL and In-House BPL. See also Access BPL, BPL, and In-house BPL.