Editing Pulse-position modulation (section)

==PPM encoding for radio control==
A complete PPM frame is about 22.5&nbsp;ms (can vary between implementation), and signal low state is always 0.3&nbsp;ms. It begins with a start frame (high state for more than 2&nbsp;ms). Each channel (up to 8) is encoded by the time of the high state plus the lower state. (PPM high state + 0.3 = servo [[Pulse-width modulation|PWM]] pulse width).

More sophisticated radio control systems are now often based on [[pulse-code modulation]], which is more complex but offers greater flexibility and reliability. The advent of 2.4&nbsp;GHz band [[frequency-hopping spread spectrum|FHSS]] radio-control systems in the early 21st century changed this further.

Pulse-position modulation is also used for communication with the [[ISO/IEC 15693]] [[contactless smart card]], as well as in the [[High frequency|HF]] implementation of the [[Electronic Product Code]] (EPC) Class 1 protocol for [[RFID]] tags.