A repeater. Repeaters work only on layer 1 (Physical) of the OSI model.
hub
multiplexer is a device that add two or more signal in a single signal in networking
A 50 Ohm Terminator is used at each end of the network to prevent signal reflections.
The network device that regenerates data signals without segmenting the network is a repeater. Repeaters are used to prevent attenuation of signals.
a passive hub does not regenerate the signal received only let it pass
A Hub is the only network device for this type of job. Since a router stops broadcasts, it segments a network in a way. On the other hand, a switch does forward broadcasts but it creates segments because each switch port can be a network on their own.
Hub
Topology
If you are referring to radio transmissions as your form of communication then it's a device that improves or boosts an incoming signal so the receiver can hear what is being said or transmitted.
Transceiver
Any technology with the possible exception to token ring may be susceptible to signal bounce when one of the cable segment is disconnected or there is a short in the wire segment. An unterminated end of a wire segment will cause signal bounce because there is no termination at one of the ends to absorb the signal, preventing it from bouncing back into the cable.