Pulse repetition frequency Pulse repetition frequency The pulse repetition frequency (PRF) is the number of pulses of a repeating signal in a specific time unit, normally measured in pulses per second. The term is used within a number of technical disciplines, notably radar. In radar, a radio signal of a particular carrier frequency is turned on and off; the term "frequency" refers to the carrier, while the PRF refers to the number of switches. Both are measured in terms of cycle per second, or hertz. The PRF is normally much lower than the frequency. For instance, a typical World War II radar like
Foot-lambert for panels in accordance with SAE AS7788. Other units of luminance: Foot-lambert A foot-lambert or footlambert (fL, sometimes fl or ft-L) is a unit of luminance in United States customary units and some other unit systems. A foot-lambert equals 1/π candela per square foot, or 3.426 candela per square meter (the corresponding SI unit). The foot-lambert is named after Johann Heinrich Lambert (1728–1777), a Swiss-German mathematician, physicist and astronomer. It is rarely used by electrical and lighting engineers, in favor of the candela per square foot or candela per square meter. The luminance of a perfect Lambertian diffuse reflecting surface