| Passbandmodulation |
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| Analog modulation |
| Digital modulation |
| Hierarchical modulation |
| Spread spectrum |
| See also |
On–off keying (OOK) denotes the simplest form ofamplitude-shift keying (ASK)modulation that representsdigital data as the presence or absence of acarrier wave.[1] In its simplest form, the presence of a carrier for a specific duration represents abinary one, while its absence for the same duration represents a binary zero.[2] Some more sophisticated schemes vary these durations to convey additional information. It is analogous tounipolar encodingline code.
On–off keying is most commonly used to transmitMorse code overradio frequencies (referred to as CW (continuous wave) operation), although in principle any digital encoding scheme may be used. OOK has been used in theISM bands to transfer data betweencomputers, for example.
OOK is morespectrally efficient thanfrequency-shift keying, but more sensitive to noise when using aregenerative receiver or a poorly implementedsuperheterodyne receiver.[3]For a given data rate, the bandwidth of aBPSK (Binary Phase Shift keying) signal and the bandwidth of OOK signal are equal.
In addition to RF carrier waves, OOK is also used inoptical communication systems (e.g.IrDA andfiber-optic communication).
In aviation, some possibly unmanned airports have equipment that let pilots key their VHF radio a number of times in order to request anAutomatic Terminal Information Service broadcast, orturn on runway lights.
OOK is also used in remote garage and gate keys, often operating at 433.92 MHz, in combination withrolling codes.
Line coding (digital baseband transmission) | ||
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| Main articles |  | |
| Basicline codes | ||
| Extended line codes | ||
| Optical line codes | ||