ANSI/IEEE Device Numbers. Protective relays are commonly referred to by standard device numbers. For example, a time overcurrent relay is designated a 51 device, while an instantaneous overcurrent is a 50 device. Multifunction relays have combinations of device numbers. A 27/59 device, for example, is a combination under/over voltage relay.
At 0Â° Celsius the speed of sound in U.S. textbooks is 331.3 m/s. At 20Â° Celsius the speed of sound then is 343.21 m/s, rounded 343 m/s. At 0Â° Celsius, the speed of sound in German textbooks is 331.5 m/s. At 20Â° Celsius the speed of sound then is 343.42 m/s, rounded 343 m/s.
Sound waves travel at a constant speed, regardless of the loudness or softness of a sound. Temperature, however, does affect their speed. At room temperature (70Â° F, or 22.2Â° C) sound travels in air at a speed of 1,129 feet (344 meters) per second.With each rise of one degree Fahrenheit, the speed increases by more than one foot per second.(With each rise of one degree Celsius, the speed increases.t room temperature (70Â° F, or 22.2Â° C) sound travels in air at a speed of 1,129 feet (344 meters) per second. With each rise of one degree Fahrenheit, the speed increases by more than one foot per second. (With each rise of one degree Celsius, the speed increases.