EST PART 1 Flashcards
Collection of electronic components and circuits designed to convert the information into a signal. It’s functions are: Encoding Compression, Error correcting operations, and Modulatation processes.
-TRANSMITTER
The reduction of signal amplitude as it passes over the transmission medium
-ATTENUATION
Random, undesirable electric energy that enters the communication. It can be also defines as any unwanted introduction of energy tending to interfere.
-NOISE
TYPES OF NOISE
- External
- Internal
It is introduces in the medium/channel and difficult to quantify.
-EXTERNAL
It is produced at the receiver resistor, diodes, transistor, wires.
-INTERNAL
TYPES OF EXTERNAL NOISE
- Industrial/man made noise
- Atmospheric/static noise
- Extraterrestrial/space noise
Occurs randomly at a frequency up to 600 MHz.
-INDUSTRIAL/MAN MADE NOISE
Caused by lightning discharges during the thunderstorms and other natural electrical disturbances occuring in earth’s atmosphere less severe above 30MHz.
-ATMOSPHERIC/STATIC NOISE
Can be observe between 8MHz to 1.5GHz.
-EXTRATERRESTRIAL/SPACE NOISE
TYPES OF INTERNAL NOISE
- Thermal noise
- Shot noise
- Flicker noise
Also called brownian noise. It is associated with the rapid and random movement of electrons within a conductor.
-THERMAL NOISE
Is caused by the random arrival of carriers at the output element of an electronic device, such as diode, FET, OR BJT
-SHOT NOISE
Noise found at low audio frequencies in transistors. Proportional to the emitter current and junction temperature. Inversely propotional to frequency.
-FLICKER NOISE
Process of altering some of the characteristics of the carrier wave by impressing the modulating signal either by amplitude, frequency, or by phase information.
-MODULATION
Is the process of recoversing the modulating signal back to modulated carrier.
-DEMODULATION
Also known as the information signal. It can be a voice/audio, picture/audio, and data.
-MODULATING SIGNAL
TYPES OF MODULATION
- Amplitude Modulation (AM)
- Angle Modulation
- Frequency Modulation (FM)
- Phase Modulation (PM)
It is a modulation process where in the amplitude of the carrier is made proportional to the instantaneous amplitude of the intelligence.
-AMPLITUDE MODULATION
It is a type of analog modulation where in the frequency or phase of the carrier is varied in accordance with the instantaneous amplitude of the modulating signal.
-ANGLE MODULATION
It is an angle modulation where the instantaneous frequency of a carrier is caused to vary by an amount proportional to the modulating signal amplitude.
-FREQUENCY MODULATION
Angle modulation where the phase angle of a carrier is caused to depart from its reference value by an amount proportional to the modulating signal amplitude.
-PHASE MODULATION
It is the process of transferring digital information (usually in binary form) between two or more points. Information that has been processed, organized, and stored is called data.
-DATA COMMUNICATION
It is a system of computers, computer terminals use to transmit and/or receive information between two or more locations.
-DATA COMMUNICATION NETWORK
These are set of rules governing the orderly exchange of data within the network or a portion of the network.
-DATA COMMUNICATION PROTOCOLS
It created the sets of rules and standards for graphics and document exchange and provide models for equipment and system compatibility, quality enhancement.
-INTERNATIONAL STANDARDS ORGANIZATION
Is one of four permanent parts of the internation telecommunications union based in geneva, switzerland.
-COMITE CONSULTATIF INTERNATIONALE DETELEGRAPHIE AT TELEPHONIE
Network and service operation, tariff and accounting principles.
-THE ITU-T
It is the name for a set of standards for communicatingamong computers. It is also to serve as a structural guideline for exchanging information between computers.
-OPEN SYSTEMS INTERCONNECTION
Adopted a seven layer communications architecture reference model. Each layer consists of specific protocols for communication.
-ISO AND ITU-T (CCITT)
It is used to amplify signals carried by a network. It is used to lengthen individual network segments to form a large extended network.
-REPEATER
Used to build a LAN by connecting different computers in a star/hierachal network topology.
-HUBS
There are two types of hubs
- Passive
- Active
The signal is forwarded as it is doesn’t need power supply.
-PASSIVE
The signal is amplified, so they work as repeaters. In fact thet have been called multiport repeaters. (uses power supply)
-ACTIVE
Connected multiple devices on a network similar to a hub, but this have the ability to remember which device is connected. It reduces traffic and divide the collision domain intto segments.
-SWITCHES
Use to extend networks by maintaining signals and traffic. It is on data link layer (ISO-OSI Model) they are capable to do data filtering and separatinh the collison domain, but they are less advanced. They are known to be used to extend distance capabilities of networks.
-BRIDGES
Used to connect different LANs od a LAN with a WAN. It controls both collision domains and broadcast domains. It work on the network layer so they can filter data based on IP addresses.
-ROUTERS
It is appropriate software to connect and translate data between networks with different protocols or architecture. It operates at the network layer and above.
-GATEWAYS
TYPES OF AREA NETWORK
- LAN
- WLAN
- WAN
- MAN
- SAN
- CAN
It is a computer network thet interconnects computers in a limited area such as a home. It is typically controlled and managed by a single person.
-LOCAL AREA NETWORK
A LAN based on wifi wireless network technology
-WIRELESS LOCAL AREA NETWORK
It is a network that covers a broad area any telecommunications network that links across metropolitan, regional, or national boundaries using a private or public network transports.
-WIDE AREA NETWORK
It is a computer network that usually spans a city or a large campus. Usually interconnects a number of local area networks using a high capacity backbone technology.
-METROPOLITAN AREA NETWORK
Sometimes called system area network. It connects servers to data storage devices through a technology like a fiber channel.
-STORAGE ARE NETWORK
Sometimes called a cluster area network. A network spanning multiple LANs but smaller than a MAN, such as on a university or local business campus.
-CAMPUS AREA NETWORK
It is transmission digital signals between the transmitter and receivers and requires physical transmission medium such as cable, fiber optic.
-DIGITAL TRANSMISSION
It is transmission of digitally modulated signals between transmitter and receivers and requires free space (air) transmission medium.
-DIGITAL RADIO
It is measure of how much information can be transmitted/propagated through a communication system. It also known as channel capacity.
-INFORMATION CAPACITY
Ideal noiseless transmission medium at a rate or equal to two times the bandwidth of the medium. The minimum theorotical bandwidth to propagate a signal is called the minimum nyquist bandwidth.
-NYQUIST THEOREM
Developed a useful relationship among bandwidth, transmission time and information capacity.
-HARTLEY’S LAW
Theoretical expression of how many bits of information per second can be transmitted without error over a communication channel with a bandwidth.
-SHANNON-HARTLEY EQUATION
It is the transmittal of digitally modulated analog signal (carrier) between two or more points in a communication system.
-DIGITAL MODULATION
TYPES OF DIGITAL MODULATION
- Amplitude Shift Keying
- Frequency Shift Keying
- Phase Shift Keying
- Quadraturre Amplitude Modulation
is the number of bits transmitted during 1 second.
-BIT RATE
Is the number of signal units per second.
-BAUD RATE
It is the simplest digital modulation techniques, where a binary information signal directly modulates the amplitude of analog carrier.
-AMPLITUDE SHIFT KEYING
It is a form of constant-amplitude angle modulation similar to standard frequency modulation.
-FREQUENCY SHIFT KEYING
It is another form of angle-modulated, constant amplitude digital modulation.
-PHASE SHIFT KEYING
It is another form of angle-modulated, varying amplitude digital modulation. It is a combination of ASK and PSK so that a maximum contrast between each signal is achieved.
-QUADRATURE AMPLITUDE MODULATION
The exchange of information through electrical/optical means between source and destination within a physically bounded medium.
-WIRE COMMUNICATION
PHYICAL TRANSMISSION MEDIA
- Metallic cable
- Twisted pair
- Coaxial cable
- Optical fiber
It is a metallic conductor system that is used to transfer electrical energy from one point to another. Used to propagete low frequency or high frequency signals.
-TRANSMISSION LINES
GENERAL TYPES OF TRANSMISSION LINES
- Balanced
- Unbalanced
Both conductors carry current for signal and return. The signal propagating down the wire is measured as the potential difference between two wires.
-BALANCED LINES
One for signal and one for ground. Ground wire may also be the reference for other signal carrying wires.The gound must go wherever the signal go.
-UNBALANCED LINES
A circuit device used to connect a unbalanced transmission line such as coax to an balanced load such as twin lead and antenna.
-BALUNS
A two paralled conductor, closely spaced and separated by air. Non conductive spacers are placed at periodic intervals for support and to keep the distance between the conductors constant generally between 2-6 inches.
-OPEN WIRE TRANSMISSION LINE
Often called ribbon cable (300ohms, impedance-balanced). Spacer between two conductors are solid dielectric.
-TWIN LEAD
Formed by twisting together two insulated conductors. Pairs are often stranded in units, and units are often cabled into cores. Neighboring pairs are twisted with different pitch to reduce interference between pairs due to mutual induction.
-TWISTED PAIR CABLE
Parallel conductor TL are suitable only for low frequency applications. It is for high frequency that reduces losses and isolate transmission paths. At high frequency, outer conductor provides excellent shielding against external interference.
-CONCENTRIC OR COAXIAL TRANSMISSION LINES
It is a cable containing one or more optical fibers. It is typically individually coated with plastic layers and contained in a protective tube suitable for the environment.
-FIBER OPTIC CABLE
Fibers are used for long distance transmission and required the use of laser as a light source, while multimode fibers can be use more types of light sources but cannot be used over long distances.
-SINGLE MODE
The cable is wheree all the light is concentrated.
-THE CORE
This is the layer of glass surrounding the core and it has the function of maintaining the light within the core itself. It provides a degree of mechanical strength and allows a more suitable size for handling purposes.
-THE CLADDING
Only one path for light to take down the cable. Extremely wide bandwidths and low losses.
-SINGLE-MODE
The light wave rays take many paths between the source and the far end of the fiber. Placed 2km between repeaters.
-MULTIMODE FIBER
The core has a uniform index of refraction providing an abrupt change in refraction index at the core cladding interface.
-STEP INDEX
The core has index of refaction that changes continuously from the center to the outside.
-GRADED INDEX
A soft silicon resin applied over the cladding in order to preserve the internet strength of the glass fiber. Without this coating, the fiber would become brittle.
-THE PRIMARY COATING
FIBER CONSTRUCTION
- Glass fiber-optic cable
- Plastic fiber-optic cable
- Plastic-clad silica
Gives off energy with a wavelength from about 300 microns down to 0.5 microns.
-LIGHT SOURCES
Non-coherent injection light sources which are low-cost, low-heat, light sources and are the most promising light sources for optical transmission.
LIGHT EMITTING DIODE
Make the most efficient use of electric energy. This coherent light source can couple a few milliwatts of light power into a fiber since it has a more direct radiation pattern.
-INJECTION LASER DIODES
When photons are absorbed by intrinsic electrons in the valence band, they add sufficient energy to generate carriers in the depletion region.
-POSITIVE INTRINSIC NEGATIVE
Light enters diode and is absorbed by the thin, heavily doped n-layer causing a high electric field intensity to e across in p-n juction.
-AVALANCHE PHOTO DIODE
