The FRU is a system component which needs to be fed from a Fiber Master Unit (FMU). It is a band selective repeater optimized for radio communication systems operating in the frequency bands 88 - 2700 MHz and is designed for use specifically in Trunked Radio as well as mobile communication Systems.

To provide radio coverage in confined areas, the RF-input/output of the repeater is connected to an antenna, radiating cable or both combined.