Repeaters
The number of nodes and the length of cable influence the quality of the signal on a network. The degradation of signal clarity is called attenuation.
Repeaters work against attenuation by repeating and cleaning up digital signals. On analog networks, devices that boost the signal are called amplifiers.
Repeaters are Physical layer (layer 1) devices on the OSI reference model.
Some repeaters can connect two physically different types of cabling, however, repeaters cannot reformat, resize, or otherwise manipulate the data packet.