ELECTRICAL NOISE AND INTERFERENCE : Definition of electrical noise Noise, or interference, can be defined as undesirable electrical signals, which distort or interfere with an original (or desired) signal. Noise could be transient (temporary) or constant. Unpredictable transient noise is caused, for example, by lightning. Constant noise can be due to the predictable 50 or 60 Hz AC 'hum' from power circuits or harmonic multiples of power frequency close to the data communications cable. This unpredictability makes the design of a data communications system quite challenging. Noise can be generated from within the system itself (internal noise) or from an outside source (external noise). Examples of these types of noise are : Internal noise Thermal noise (due to electron movement within the electrical circuits) Imperfections (in the electrical design). Shot noise is generated by individual electrons "jumping" across some sort of barrier potential as they travel ...
