Any carrier of information; opposed to noise. See carrier wave.

The measured value recorded by a pixel during a CCD integration. The signal in a CCD image usually comprises input from sky, thermal, and electronic sources. The natural degree of randomness in the pixel value is the noise component of the signal.

THAT PART OF THE VARIATION OF THE ENVIRONMENT WHICH CORRESPONDS TO A REAL - PHYSICAL PHENOMENON. WHEN THE SIGNAL IS LARGE - ITS SIGNATURE STANDS OUT ABOVE THE REMAINDER TO THE VARIATION OF THE ENVIRONMENT - CALLED THE NOISE. SIGNAL IS SOMETIMES PREDICTABLE. NOISE IS NOT. THE RELATIONSHIP BETWEEN SIGNAL AND NOISE IS EXPRESSED AS A NUMBER - CALLED THE SIGNAL-TO-NOISE RATIO OR S/N. WHEN S/N IS GREATER THAN 1 - SIGNAL IS LARGER THAN NOISE - AND THE SIGNATURE OF THE DISTURBANCE CAUSING THE SIGNAL CAN BE SEEN. WHEN S/N IS LESS THAN 1 WE HAVE NO HOPE OF SEEING OR PREDICTING THE DISTURBANCE.

used in context of a data series, this term pertains to the the 'true' value each data point should take in the set. For many reasons, the true signal in data can be hidden by the associated noise. Reasons for this phenomenon could be as simple as inaccurate data collection or recording methods, or as complex as masking resulting from unclear differentation of data sources or classes. This makes forecasting the data more difficult and sometimes impossible.

One of two results in any experiment; the signal is the effect on the data caused by the experimental factor that one is investigating, for example, in an ESP experiment, the signal is the the number of correct guesses due to ESP; see also Noise.

That component of a measurement that the user wants to see – the response from the targets, from the earth, etc. (See also noise)

Signal Path Signal To Noise Ratio