thumb|the duty cycle d is defined as the ratio between the pulse duration (\tau) and the period (p) of a rectangular waveform thumb|spectrum in relation to duty cycle a duty cycle is the percentage of one period in which a signal is active. a period is the time it takes for a signal to complete an on-and-off cycle. as a formula, a duty cycle may be expressed as: :d = \frac{t}{p} \times 100\% where d is the duty cycle, t is the time the signal is active, and p is the total period of the signal. thus, a 60% duty cycle means the signal is on 60% of the time but off 40% of the time. the "on time" for a 60% duty cycle could be a fraction of a second, a day, or even a week, depending on the length of the period. duty cycles can be used to describe the percent time of an active signal in an electrical device such as the power switch in a switching power supply or the firing of action potentials by a living system such as a neuron. == applications == === electrical devices === electrical motors typically use less than a 100% duty cycle. for example, if a motor runs for one out of 100 seconds, or 1/100 of the time, then, its duty cycle is 1/100, or 1 percent.{{cite web|url=http://www.electricmotors.machinedesign.com/guiedits/content/bdeee1/bdeee1_3.aspx|title=electric motors|publish
Mechanical_engineering Timing_in_electronic_circuits