A repeater is a device that has single input and output ports, and makes it possible for signals to be transmitted across a network for long distances by conditioning the received signal and retransmitting the conditioned signal to the various segments while a hub is simply a repeater with multiple input and multiple output ports. Both hubs and repeaters strengthen an incoming data signal by regenerating it to reach its destination. Otherwise, the data signal will be subjected to attenuation.
Attenuation is a term used to describe the gradual weakening of a data signal as it travels farther away from the transmitter. Repeaters and hubs normally operate at the physical level of the Open Systems Interconnection, or OSI, model, and they are not meant to direct signals to a specific destination as switches and routers do. To pass data signal through the repeater from a segment to another successfully, the packets and the LLC, or Logical Link Control, protocols should be similar on every segment. Therefore, a repeater will not initiate any communication between any two segments, such as between a Token Ring, or 802.5 segment, and an Ethernet, or 802.3 segment. On the other hand, using a hub leads to a single broadcast domain because when a host sends a broadcast, all other hosts in the hub hear it.