All transmission media attenuate (weaken) the electromagnetic
waves that travel through the media. Attenuation therefore limits the distance
any medium can carry data. Adding a device that amplifies the signal can allow
it to travel farther, increasing the size of the network. For example, if one
is connecting computers that are more than 100 meters apart using Ethernet
cable, one will need a device that amplifies signals to ensure data
transmission. Devices that amplify signals in this way are called repeaters.
Repeaters are fall into the following categories:
a) Amplifiers
b) Signal-regenerating
devices (Repeaters)
Amplifiers
Amplifiers simply
increase the power of the incoming signal, i.e. both signal and the noise.
These are able to improve signal to noise in the analog type systems only.
Signal
regenerating repeaters
Signal
regenerating repeaters create an exact duplicate of the incoming digital data
by identifying it amidst the noise, reconstructing it and passing only the
desired information. In this manner, the original signal is duplicated, boosted
to its original strength and then sent.
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