EXTERNAL NOISE, INTERNAL NOISE:
It is a Noise generated outside the device or circuit. There are three primary sources of external noise.
(i) Atmospheric ,
(ii) Extra terrestrial and
(ii) Manmade noise.
Extraterrestrial Noise consists of electrical signals that originate from outside earths atmosphere and is therefore also called as deep space noise. This noise originates from the milky way , other galaxies and the sun.
Extraterrestrial noise is subdivided into two categories.: (i) Solar and (ii) Cosmic.
Internal Noise: It is the noise caused by electrical interference generated within a device or circuit.
(ii) Shot ,Transits time.