Lightning,Power Surges,and other electro-magnetic interference can introduce unwanted electrical currents in the electronic components or wires used for communication.Interference that is severe especially lightning can cause permanent damage to network equipment.More often,however interference merely changes the signal used for transmission without damaging the equipment.A small change in the electrical signal can cause the receiver to misinterpret one or more bits of the data.In fact,interference can completely destroy a signal,meaning that although the sender transmits,the receiver does not detect that any data has arrived.Surprisingly,interference on a completely idle transmission circuit can create the opposite effect that means the sender does not transmit any thing,a receiver might interpret the incoming interference as a valid sequence of bits or characters.All these types of errors are known as transmission errors.In the last we can summarize the whole thing in this way that much of the complexity in the computer networks arises because digital transmission system are susceptible to interference that can cause random data to appear or transmitted data to be lost or changed.
Sunday, December 21, 2008
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