Repeaters (Computer Network)

 Repeaters -

A repeater ( or regenerator ) is an electronic device that operates on only the physical layer of the OSI model. Signals that carry information within a network can travel a fixed distance before attenuation endangers the integrity of the data. A repeater installed on a link receivers the signal before it become too weak or corrupted, regenerates the original bit pattern. and puts the refreshed copy back onto the link.

        A repeater allows us to extend only the physical length of a network. the repeater does not change the functionality of the network min any way. The two sections connected by the repeater in figure are , in reality, one network, if station A sends a frame to station B, all stations (including C and D) will receive the frame

 

just as they would without the repeater. The repeater does not have the intelligence to keep the frame from passing to the right 

side when it is meant for a station of the left. The difference is that, with the repeater, stations C and D receive a truer copy of the frame than would otherwise have been possible.

Not an Amplifier :

It is tempting to compare a repeater to an amplifier, but the comparison is inaccurate. An amplifier cannot discriminate between the intended signal and noise; it amplifier equally everything fed into it. A repeater does not amplify the signal, it regenerates it. when it receives a weakened or corrupted signal, it creates a copy bit for bit, at the original strength. A repeater is a regenerator, not an amplifier. 

The location of a repeater on a link is vital. A repeater must be placed so that a signal reaches it before any noise changes the meaning of any of its bits. A little noise can alter the Precision of a bit's voltage without destroying its identity. If the computed bit travels much farther, however, accumulated noise can change its meaning completely.