(1) In print and copy terminology, duty cycle refers to the number of copies or prints that the device can reliably produce on a monthly basis. Exceeding the duty cycle number on a regular basis can lead to equipment malfunctions and breakdowns over time. Alternatively, not printing or copying in numbers close to the duty cycle could mean you have over-purchased on equipment.
(2) In time measurement, duty cycle is defined as the ratio of the duration of the phenomenon in a given period to the period, where duty cycle is abbreviated as D. In electronics, for example the duty cycle would refer to the period of time in which the device operates without negative effects (e.g. the period of time a power supply would run without overheating).
(3) In RF (radio frequency) the duty cycle, also called the duty factor, is the measure of the fraction of the time a radar is transmitting.