On–off keying

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.^[1] 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.

On–off keying is most commonly used to transmit Morse code over radio frequencies (referred to as CW (continuous wave) operation), although in principle any digital encoding scheme may be used. OOK has been used in the ISM bands to transfer data between computers, for example.

OOK is more spectrally efficient than frequency-shift keying, but more sensitive to noise when using a regenerative receiver or a poorly implemented superheterodyne receiver.^[2] For a given data rate, the bandwidth of a BPSK (Binary Phase Shift keying) signal and the bandwidth of OOK signal are equal.

In addition to RF carrier waves, OOK is also used in optical communication systems (e.g. IrDA and fiber-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 an Automatic Terminal Information Service broadcast, or turn on runway lights.

OOK is also used in remote garage and gate keys, often operating at 433.92 MHz, in combination with rolling codes.

References

^ Simple Binary Modulation – One Bit at a Time
^ L. ASH, DARRELL (1992). "A comparison between ook ask and fsk modulation techniques for radio links" (PDF). RF Monolithics. p. 6. Archived from the original (PDF) on 19 August 2019. Retrieved 24 February 2015.

External links

"Application Note 4439 - I'm OOK. You're OOK?". Maxim Integrated. 2009.

[1] Simple Binary Modulation – One Bit at a Time

[2] L. ASH, DARRELL (1992). "A comparison between ook ask and fsk modulation techniques for radio links" (PDF). RF Monolithics. p. 6. Archived from the original (PDF) on 19 August 2019. Retrieved 24 February 2015.

[1]

[2]

v t e International Morse code
Transmission methods	Electrical telegraph On–off keying Continuous wave Modulated continuous wave Heliograph Signal lamp
Notable signals	SOS CQD Morse code mnemonics Prosigns for Morse code Morse code abbreviations Q code Z code
Other writing systems in Morse code	American Morse code Greek alphabet Cyrillic script Russian Hebrew script Arabic script Wabun code Chinese telegraph code

v t e Line coding (digital baseband transmission)
Main articles	Unipolar encoding Bipolar encoding On–off keying Mark and space
Basic line codes	Return to zero (RZ) Non-return-to-zero, level (NRZ/NRZ-L) Non-return-to-zero, inverted (NRZ-I) Non-return-to-zero, space (NRZ-S) Manchester Differential Manchester/biphase (Bi-φ)
Extended line codes	Conditioned diphase 4B3T 4B5B 2B1Q Alternate mark inversion Modified AMI code Coded mark inversion MLT-3 encoding Hybrid ternary code 6b/8b encoding 8b/10b encoding 64b/66b encoding Eight-to-fourteen modulation Delay/Miller encoding TC-PAM
Optical line codes	Carrier-suppressed return-to-zero Alternate-phase return-to-zero
See also: Baseband Baud Bit rate Digital signal Digital transmission Ethernet physical layer Pulse modulation methods Pulse-amplitude modulation (PAM) Pulse-code modulation (PCM) Serial communication Category:Line codes