In telecommunication, the term duty cycle has the following meanings:

1. In an ideal pulse train , i.e., one having rectangular pulses, the ratio of the pulse duration to the pulse period .

Note: For example, the duty cycle is 0.25 for a pulse train in which the pulse duration is 1 μs and the pulse period is 4 μs.

2. The ratio of (a) the sum of all pulse durations during a specified period of continuous operation to (b) the total specified period of operation.

3. In a continuously variable slope delta (CVSD) modulation converter, the mean proportion of binary "1" digits at the converter output in which each "1" indicates a run of a specified number of consecutive bits of the same polarity in the digital output signal.

4. In a periodic phenomenon, the ratio of the duration of the phenomenon in a given period to the period.

Note: In a piece of electrical equipment, e.g., an electric motor, the period for which it may be operated without deleterious effects, e.g., from overheating.

Source: from Federal Standard 1037C and from MIL-STD-188