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RECS (Renewable Energy Certificates System)

RECS was introduced in 2002 to promote the development of renewable energies at international level. The system now operates in 24 countries in Europe as well as in Canada, the U.S. and South Africa. The standard certificate awarded by RECS guarantees that identifiable amounts of electrical energy are supplied from specific regenerative sources, thus making regenerative, CO2-neutral energy freely tradable. Procurement of these certificates when buying energy means that the quantities purchased can be traced directly to the certificate acquirer. Deutsche Telekom relies on this system to obtain all the energy it needs in Germany from regenerative sources.


Rectifiers are used in electrical engineering and electronics to convert AC (alternating current) into DC (direct current).

Relative energy consumption

In contrast to absolute energy consumption, the relative energy consumption is calculated in relation to a specified reference value. This may be the number of consumers, for example, or a company's revenues.

Remote control connection

A remote control connection is used to transmit electronic data across large distances, e.g., via satellite. For example, it is used in network control systems to transfer network data between the switch and a control unit.


A feature of cellular mobile communications networks that ensures that activated mobile stations remain accessible, regardless of location, in all radio cells of the entire area served by the network. Roaming  can also include similar networks run by different operators, as is the case with international roaming within the pan-European GSM system.


A router is an interface between two networks. Several networks are connected to each other via a device with network connections and configurable software. This device analyzes the incoming data packets based on their destination addresses, and blocks them or forwards them.

RRH/RRU systems (Remote Radio Head/Remote Radio Unit)

RRH or RRU systems are used for weatherproof installation of transmission and receiver systems directly onto antenna masts for mobile communications. They need only a short high-frequency line to connect the antenna, which allows reduced transmission power and increased efficiency.