Subtractive noise systems

E represents the combined collection and detection efficiency of the system and F the intrinsic photon-economy of the technique. The factor 77 accounts for the subtractive noise, tA is the dead-time of the detector and Q the count rate of the system. 

Block diagram of a spectral-subtraction noise-reduction system. 265... 

The traditional method of noise subtraction has been revived and used very effectively for ion spectroscopy.°9 The laser beam is split into two parts, one for spectroscopy and the other for reference and detected by two matched infrared detectors. The signals from the two infrared detectors are elctronically combined with opposite phase to subtract noise. This method is particularly effective for a color center laser and a difference frequency laser system where the... 

This necessitates plant capable of control of temperature by being able to add or subtract heat from the air and control of humidity by being able to add or subtract moisture. The system also comprises fan(s), filtration, and a distribution system and may include noise control. Other terms such as cooling or comfort cooling may be met and these can be taken to mean an ability to lower the temperature of the air by refrigeration but without full control of humidity. Moisture may be removed as an incidental characteristic of the cooling coil. The term air conditioning is sometimes used where control of humidity is not included. It is essential to employ clear specifications of performance. 

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