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Electromagnetic Spectrum
Ranges from 30 Hz to several GHz

FCC has jurisdiction over the use of this spectrum
Bandwidth
Range of frequencies that can be transmitted with minimal distortion

Measure of transmission capacity of communications medium

Analog: BW is expressed in HZ
Digital: BW is expressed in bps
Hartley's Law
The amount of information that can be transmitted is directly proportional to bandwidth and transmission time

I = ktBW
Broadband
Simultaneous transmission of multiple channels over a single line

Originated in the CATV industry
Baseband
Digital transmission of a single channel

Low cost, ease of installation, and high transmission rates
Serial Communication
Bit serial transmission

Synchronization problem at: bit, word, frame level

Signal transitions occur according to a transmitter clock
Two types of Serial Communications
Asynchronous
Synchronous
Asynchronous
Transmitter and receiver clocks are independent
Synchronous
Transmitter and receiver are synchronized
Asynchronous Transmission
Transmission Rate (9600bps, 19200bps, etc)

Number of stop bits (1, 1.5, 2)

Word length (usually 8 bits)
Simplex
In only one direction from transmitter to receiver

Eg. Radio
Half-duplex
Two-way communications, but only in one direction at a time

Eg. Walkie-Talkie
Full-duplex
Simultaneous two-way communication

Eg. Video-conferencing
Serial
Transmitting bits one after another along a single path

Slow, cost-effective, has relatively few erorrs, practical for long distances
Parallel
Transmitting a group of bits at a single instant in time, requires multiple paths

Fast but expensive, practical for short distances
UART
Universal Asynchronous Receiver Transmitter
- Parallel to Serial converter
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