Telecommunication Technologies

Overview
Telecommunication technology might seem like a formidable challenge, but it's quite a simple foe when it comes down to it. There's just a few things to know and you'll be ready for anything!

Three basic elements of a system

 * Transmitter
 * Takes information and converts it into a signal (to be transmitted)
 * Medium
 * Carries the signal
 * Receiver
 * Receives the signal and converts it back into usable information

Networks and Channels

 * Network
 * A collection of a transmitters and receivers that support the transfer of information
 * Channel
 * A division in a transmission medium so that multiple streams of information can be sent at once

Circuits

 * Circuit
 * A path over a medium between at least two points, between a transmitter and a receiver
 * Can also refer to an electronic path used for signal transfer (an application of the general idea of a circuit)

Circuit Types

 * Dedicated
 * Directly connects devices in a network without accessing a switch
 * Path is available 24/7 for use by a designated user (an individual or a company)
 * Available on a private or leased basis
 * An example of a dedicated circuit is the direct phone line from the US to Russia
 * Switched
 * Circuit is temporarily established, at the request of a station connected to the circuit
 * Connected on a flexible basis through one or more switches
 * A switch is a device that establishes, maintains, and changed logical connections over physical circuits
 * Virtual
 * Refers to a logical connection (rather than a physical one) over which data from a source is passed to a destination over various real circuit configurations during one period of communication
 * A generalized (abstracted) form of a circuit that can be applied to many physical examples of circuits
 * Can be fixed (permanent) or dynamical determined at the time of transmission (switched)

Measuring Capacity

 * Hertz
 * Cycles per second of a periodic phenomena (usually a wave)
 * So if a wave repeats 8 times per second (that is that the waveform "restarts" 8 times in 1 second), we measure the wave to have 8 Hz
 * Baud
 * How many signal elements are sent in 1 second
 * Although 8 bits are sent in the example below, we measure it as 4 baud, as the signaling element only signals 4 changes
 * Bps (bits per second)
 * How many bits are sent in 1 second
 * In the example below we can clearly count 8 bits sent during the 1 second period, so we measure it as 8bps or 8 bits per second.

Types of Bandwidth

 * Narrowband
 * A transmission channel with a single voice channel (usually 4kHz or less, 64kbps or less)
 * Wideband
 * A transmission channel with wider bandwidth than one voice channel (usually used to contrast narrowband)
 * Broadband
 * A transmission channel more than 64kbps, usually can also provide multiple channels of data over a single medium

Analog vs. Digital

 * Analog
 * Signal is analogous to the original information
 * Measured in Hz
 * Uses amplifier to boost signal for transmission over some distance
 * Pros
 * Continuous flow - easy to recover
 * Natural way that people create and consume signals
 * Widely available
 * Cons
 * The more information, the more bandwidth required
 * Noise (excess data that contains no information)
 * Insecure
 * Digital
 * Information converted to 1s and 0s (pulse signals)
 * Measured in bps (bits per second)
 * Uses repeaters to boost signal over distance
 * Pros
 * Increased efficiency through compression
 * Enhanced security
 * Improved error performance, therefore higher quality
 * Cons
 * Relatively high cost (in comparison to analog)
 * Upgradeability / Scalability
 * Attenuation, noise

Converting Digital and Analog Signals

 * Modem (Modulator demodulator)
 * modulated outgoing digital signals from a computer or device to analog signals
 * demodulated incoming analog signals and converts it into a digital signal for the digital device
 * Codecs
 * Coder/decoder
 * Standardized conversion of analog signals into digital form to send on a digital circuits
 * Usually compresses them in order to conserve bandwidth on a transmission path

CONTINUE...

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