Converting Bits to Signals

There are two fundamentally different ways to produce digital signals
DC or lowpasswhere bits are represented using square waves.
Common encoding schemesinclude:

• Non-return-to-zero (NRZ)

• Bipolar

• Manchester

Bandpassor modulatedwhere bits are represented using fixed frequency sinusoids. This is used when the channel does not pass low frequency signals.
Common modulation techniquesinclude:

• Amplitude shift keying (ASK)

• Frequency shift keying (FSK)

• Phase shift keying (PSK)