Keying (telecommunications)

Passband modulation
Analog modulation
AM FM PM QAM SM SSB
Digital modulation
ASK APSK CPM FSK MFSK MSK OOK PPM PSK QAM SC-FDE TCM WDM
Hierarchical modulation
QAM WDM
Spread spectrum
CSS DSSS FHSS THSS
See also
Capacity-approaching codes Demodulation Line coding Modem AnM PoM PAM PCM PDM PWM ΔΣM OFDM FDM Multiplexing
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Keying is a family of modulation forms where the modulating signal takes one of a specific (predetermined) number of values at all times. The goal of keying is to transmit a digital signal over an analog channel. The name derives from the Morse code key used for telegraph signaling.

Modulation is the general technique of shaping a signal to convey information. When a digital message has to be represented as an

used). This is in contrast to analogue modulation, where an analogue signal is transmitted over an analogue channel, and where the modulated analogue signal will have an infinite number of meaningful states. Furthermore, note that keying or digital modulation applies to transmitting a digital signal over an analogue .

Several keying techniques exist, including phase-shift keying, frequency-shift keying, and amplitude-shift keying. Bluetooth, for example, uses phase-shift keying to exchange information between devices.

An overview of keying techniques is given at Modulation § Fundamental digital modulation methods.