The automatic cab signal system shall be arranged so that cab signals will be continuously controlled in accordance with conditions described in Â§ 236.205 that obtain at least stopping distance in advance. Â§ 236.512 Cab signal indication when locomotive enters block where restrictive conditions obtain.
Dissolved oxygen (DO) is a measure of the quantity of free oxygen molecules in water. The concentration of DO is an important indicator of the health of an aquatic ecosystem because oxygen is essential for almost all forms of life. Oxygen is necessary for respiration and for some chemical reactions.
Percent saturation is the measured dissolved oxygen level divided by the greatest amount of oxygen that the water can hold under various temperature and atmospheric pressure conditions multiplied by 100. Left: This graph shows the maximum amount of oxygen that can be dissolved in water at different temperatures.hoto: Courtesy of Dr. Ben Stout. One measure of dissolved oxygen in water is parts per million (ppm), which is the number of oxygen molecules (O 2) per million total molecules in a sample. Calculating the percent saturation is another way to analyze dissolved oxygen levels.