Couplers provide the means to transmit on and receive the communication signals from the electric power line. There are two methods for coupling the signal to the line - capacitive and inductive coupling.

An ICU (Inductive Coupling Unit) is a piece of equipment to place communication signals in the 2 MHz- to 40-MHz range onto a distribution line and a key device in the PLC system. A current of several hundred amperes is being applied to a medium-voltage distribution line at a voltage of 6.6 to 35 kV.
Since the ICU is capable of achieving signal coupling with the distribution line without contact required, it is characterized by high reliability and ease of installation on existing distribution lines.

Single phase capacitive couplers are widely used for coupling to LV networks.
These capacitors are relatively inexpensive and are simple to connect.
In most cases this requires an outage of the LV circuit, however, it is possible to use insulation piercing connectors to make the connection to the LV circuit and these may be fitted live.