The idea of using power lines also for communication purposes has already been around at the beginning of the last century. It is now broadly referred to as power line communications (PLCs). The obvious advantage is the widespread availability of electrical infrastructure, so that theoretically, deployment costs are confined to connecting modems to the existing electrical grid. Power line technologies can be grouped into the following: ultra narrowband (UNB) technologies operating at very low data rate in the ULF band (0.3-3 kHz) or in the upper part of the SLF (30-300 Hz) ; narrowband (NB) technologies operating in the VLF, the LF and in parts of the MF bands (3-500 kHz), and capable of data rates ranging between a few kbit/s and around 500 kbit/s ; and broadband (BB) technologies operating in the MF, HF or VHF bands (1.8-250 MHz) and presenting a PHY rate ranging from several Mbit/s to several hundred Mbit/s. This chapter provides an overview of current NB-PLC and BB-PLC systems.