Digital Transmission

Analog signals: continuous with infinitely many levels

Digital signals: discrete with finite levels

Encoding data in binary as voltages that can be transmitted over wires.

Encoding methods

1. Non-return to zero (NRZ)
2. Return to zero (RZ)
3. Manchester

Encoding Method	Illustration
NRZ
RZ
Manchester

Analog Transmission

Represented as wave, e.g. sine wave

• $A$ for amplitude
• $f$ for frequency
• $\phi$ for phase (like a shift or offset for the signal from the reference time.)

Bandwidth: The difference between the highest and lowest frequency that can pass through a channel

Signal to Noise Ratio: The strength of signal over noise.

At the signal receiver side, the signal is sent to a sort of comparator circuit as shown above.

Shannon Channel Capacity: The theoretical maximum bit rate of a noisy channel

Modem: Modulator/Demodulator

Encoding methods

1. Amplitude Shift Keying
2. Frequency Shift Keying
3. Phase Shift Keying