Gap filler are terms derived from an English term designating an interconnection of the American metro of certain cities. For the telecommunications universe, the expression refers to a type of contribution link particularly suited to broadcasting.
The specificity of the equipment it uses allows it to repeat (re-transmit) portions of the radio spectrum with or without amplification. In digital broadcasting, it does not modify the composition of the (multiplex) bouquets of each frequency or channel retransmitted.
These transmitter / repeater solutions are considerably more economical than re-transmitters because of the small number of devices operated.
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