On-off keying (
OOK) denotes the simplest form of
amplitude-shift keying (ASK)
modulation that represents
digital data as the presence or absence of a
carrier wave. In its simplest form, the presence of a carrier for a specific duration represents a
binary one, while its absence for the same duration represents a binary zero. Some more sophisticated schemes vary these durations to convey additional information. It is analogous to
unipolar encoding line code.