Signals travel through the transmission media, which are not perfect. The imperfections cause impairment in signal. This means that the signal at the beginning and end of the medium are not same. What is sent in and what is received. There are three types of impairment usually occur. These are attenuation, distortion and noise. Attenuation means the loss of energy. When a signal, simple or composite, travels through a medium, it loses some of its energy so that it can overcome the resistance of the medium. That is why a wire carrying electrical signals gets worm, if not hot, after a while. Some of the electrical energy in signal is converted to heat. To compensate for this loss, the amplifiers are used to amplify the signal.
Distortion means that signal changes its form or shape. Distortion occurs in a composite signal that is made of different frequencies. Each signal component has its own propagation speed through a medium and, therefore its own delay in arriving at the final destination. Noise is another problem occurred during the transmission of data. Several types of noise like thermal noise, induced noise, crosstalk, and impulse noise may corrupt the signal. Thermal noise is the random motion of electrons in a wire which creates an extra signal not originally sent by the transmitter. Induced noise comes from the sources such as motors and appliances. These devices act as a sending antenna and transmission medium acts as the receiving antenna. Crosstalk is the effect of one wire on other.
Distortion means that signal changes its form or shape. Distortion occurs in a composite signal that is made of different frequencies. Each signal component has its own propagation speed through a medium and, therefore its own delay in arriving at the final destination. Noise is another problem occurred during the transmission of data. Several types of noise like thermal noise, induced noise, crosstalk, and impulse noise may corrupt the signal. Thermal noise is the random motion of electrons in a wire which creates an extra signal not originally sent by the transmitter. Induced noise comes from the sources such as motors and appliances. These devices act as a sending antenna and transmission medium acts as the receiving antenna. Crosstalk is the effect of one wire on other.
