A more typical value is . The importance of propagation delay varies widely with the length of the channel. The effects of noise on a signal Impulse noise is common in low-frequency circuits and arises from electric fields generated by electrical switching. It appears as bursts at the receiver, and when present can have a catastrophic effect due to its large power. When radio links are used, interference from other transmitters can be problematic.
Thermal noise is always present.
It is due to the random motion of electric charges present in all media. It can be generated externally, or internally at the receiver. Equation says that hot systems generate more noise. A bit error in a transmitted signal due to channel effects Communications channels can be a physical connection between correspondents. Wires, coaxial cables and optical fibres are used for this purpose.