noise factor of a system is defined as
Noise figure The noise factor is defined as the ratio of the output noise power of a device to the portion thereof attributable to thermal noise in the input termination at standard noise temperature T0 (usually 290Â K). The noise factor is thus the ratio of actual output noise to that which would remain if the device itself did not introduce noise, or the ratio of input SNR to output SNR.
Peripheral nervous system The peripheral nervous system is divided into the somatic nervous system, and the autonomic nervous system. The somatic nervous system is under voluntary control, and transmits signals from the brain to end organs such as muscles. The sensory nervous system is part of the somatic nervous system and transmits signals from senses such as taste and touch (including fine touch and gross touch) to the spinal cord and brain. The autonomic nervous system is a 'self-regulating' system which influences the function of organs outside voluntary control, such as the heart rate, or the functions of the digestive system.