L

L - Symbol for inductance.

Laminated Cable - Insulated or uninsulated wires which are encapsulated by two sheets of laminate material to maintain a predetermined pitch.

LAN - A data network connecting any number of users, intended to serve a small area. Local Area Network. A group of computers and associated devices that share a common communications line and typically share the resources of a single processor or server within a small geographic area.

Laser - A coherent source of light with a narrow beam and a narrow spectral bandwidth (about 2nm).

Lay - The length measured along the axis of a wire or cable required for a single strand (in stranded wire) or conductor (in cable) to make one complete turn about the axis of the conductor or cable. In a twisted pair cable, the lay length is the distance it takes for the two wires to completely twist around each other.

Lay Direction - The direction of the progressing spiral twist in a cable while looking along the axis of the cable away from the observer. The lay direction can be either "left" or "right".

Lead Dress - The placement or routing of wiring and component leads in an electrical circuit.

Lead-in - The cable that provides the path for r-f energy between the antenna and the receiver or transmitter.

Leakage - The undesirable passage of current over the surface of or through an insulator.

LEC - Local Exchange Carrier.

Level - A measure of the difference between a quantity or value and an established reference.

LF - Low frequency.

Line Drop - A voltage loss occurring between any two points in a power or transmission line. Such loss, or drop, is due to the resistance, reactance, or leakage of the line.

Line Equalizer - A reactance (inductance and/or capacitance) connected in series with a transmission line to alter the frequency-response characteristics of the line.

Line Level - Refers to the output voltage level of a piece of electronic equipment. Usually expressed in decibels (e.g.. 0dBv).

Line Voltage - The value of the potential existing on a supply or power line.

Link - The horizontal cable including the workstation outlet and patch panel in the telecommunications closet plus two meters of cable at each end for testing.

LMDS - Local Multipoint Distribution Service

Load - A device that consumes power from a source and uses that power to perform a function.

Loaded Line - A transmission line that has lumped elements (inductance or capacitance) added at uniformly spaced intervals. Loading is used to provide a given set of characteristics to a transmission line.

Loading - A transmission line that has lumped elements (inductance or capacitance) added at uniformly spaced intervals. Loading is used to provide a given set of characteristics to a transmission line.

Local Area Network - A data network connecting any number of users, intended to serve a small area.

Long-wire Antenna - Any conductor length in excess of one-half of a wavelength. In a residential television installation, a horizontal run or unshielded lead-in will act as a long-wire antenna and introduce additional signal on top of the regular antenna signal causing ghosts.

Loss - Energy or signal lost without accomplishing useful work.

Low Frequency - A band of frequencies extending form 30 to 300 kHz in the radio spectrum, designated by the Federal Communications Commission.

Luminance Signal - The portion of the composite video signal that represents the brightness or the black and white information.


M

MAC - Media Access Control (layer of OSI Reference Model).

MAN - A data network intended to serve the area of a city or an area of similar size.

Manufacturing Automation Protocol - A manufacturing automation protocol based on IEEE 802.4 standards.

MAP - A manufacturing automation protocol based on IEEE 802.4 standards.

Margin - Distance between reference edge of cable and nearest edge of first conductor or center of first conductor.

Mass-Termination - The process of simultaneously terminating all conductors in a single operation.

Matte Finish PVC - A special formulation of PVC which very closely looks and feels like rubber.

MATV - Abbreviation for Master Antenna Television.

MB - Megabyte.

Mbps - Mega bits per second - the number of bits, in millions, transmitted per second.

Mega - Prefix meaning million.

Megahertz (MHz) - Unit of frequency equal to one million hertz (one million hertz per second).

Metropolitan Area Network - A data network intended to serve the area of a city or an area of similar size.

mFd - Microfarad (one-millionth of a farad).

MHz - Megahertz.

Micro - Prefix meaning one-millionth.

Micron - Millionth of a meter.

Microphonics - Noise caused by mechanical excitation of a system component. In a single-conductor microphone cable, for example, microphonics can be caused by the shield rubbing against the dielectric as the cable is flexed.

Mil - A unit of length equal to one thousandth of an inch (.001").

Milli - Prefix meaning one-thousandth.

MMDS - Multichannel Multipoint Distribution Service.

Mode - A single electromagnetic wave traveling in an optical fiber.

Modem - Device that converts signals in one form to another form compatible with another kind of equipment.

Modulation - Altering the characteristics of a carrier wave to convey information. Modulation techniques include amplitude frequency, phase, plus many other forms of on-off digital coding.

Molded Cable - Cable assemblies with molded connectors on one or both ends.

Mono Filament - A single strand filament as opposed to a braided or twisted filament.

MSO - Multiple System Operator.

MTP - Simple Mail Transfer Protocol.

Multi-Conductor Cable - Cable with more than one conductor.

Multiplex - A technique for putting two or more signals into a single channel.

Mutual Capacitance - Capacitance between two conductors when all other conductors are connected together and grounded.

mV - Millivolt (one-thousandth of a volt).

mW - Milliwatt (one-thousandth of a watt).


N

Nano - One-billionth.

Nanometer (nm) - One billionth of a meter.

Nanosecond - One billionth of a second.

National Electrical Code (NEC) - A publication of the National Fire Protection Association (NFPA) which outlines requirements for electrical wiring and building construction. Also called the NEC.

NEC - A publication of the National Fire Protection Association (NFPA) which outlines requirements for electrical wiring and building construction. Also called the NEC.

NEMA - National Electrical Manufacturers Association.

Neoprene - A synthetic rubber with good resistance to oil, chemical, and flame. Also called polychloroprene.

Network - A network is a method of data communications between computers.


NEXT - Near end Crosstalk (dB) - Crosstalk induced on the pairs, measured at the end "near" the transmitter.

NFPA - National Fire Protection Association.

Nibble - One half byte (4 bits).

Noise - In a cable or circuit, any extraneous signal which tends to interfere with the signal normally present in or passing through the system.

Non-Paired Cable - Cable with two or more cabled conductors that are not in a paired configuration.

Non-Plenum - Area that a cable can be installed in a building that is not used for air return.

Numerical Aperture (NA) - A measure of the angular acceptance for a fiber. It is approximately the sine of the half-angle of the acceptance cone.

Nylon - An abrasion-resistant thermoplastic with good chemical resistance.


O

OFHC - Abbreviation for oxygen-free, high conductivity copper. It has 99.95% minimum copper content and an average annealed conductivity of 101% compared to standard copper.

Ohm - The unit of electrical resistance. The value of resistance through which a potential difference of one volt will maintain a current of one ampere.

Optical Waveguide Fiber - A transparent filament of high refractive index core and low refractive index cladding that transmits light.

OSI - Open System Interconnect (Model for networking protocols).

Output - The useful power or signal delivered by a circuit or device.

P

Paired Cable - Cable with conductors cabled in groups of two.

Parallel Circuit - A circuit in which the identical voltage is presented to all components, with current dividing among the components according to the resistances or the impedances of the components.

Parallel Digital - Digital information that is transmitted in parallel form. Often used informally to refer to parallel digital television signals.

Patchcord - A flexible piece of cable terminated at both ends with plugs. Used for interconnecting circuits on a patchboard.

PE - Polyethylene.

Peak - The maximum instantaneous value of a varying current or voltage.

Phase - An angular relationship between waves.

Phase Shift - A change in the phase relationship between two alternating quantities.
multiplication of carriers in the junction region. The advantage in using an APD is its higher signal-to-noise ratio, especially at high bit rates.

Physical Layer - The actual portion of a network that is used to physically connect computers of a network and over which the data is transmitted - the cable.

PIC - Plastic Insulated Conductor. Provides strong insulation.

Pico - One-trillionth.

Plenum - A compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system.

Plug - A male housing with male or female contacts.

Point-to-Point Wiring - Wiring that consists of continuous conductors terminated at each end to circuit destination.

Polarization - The orientation of a flat cable or a rectangular connector. e.g., for gray flat cable, the colored edge indicating the number one conductor.

Polyethylene - A thermoplastic material having excellent electrical properties. Low dielectric constant, a stable dielectric constant over all frequencies, very high insulation resistance. In terms of flexibility, polyethylene can be rated stiff to very hard, depending on molecular weight and density - low density being the most flexible and the high-density, high-molecular weight formulation being very hard. Moisture resistance is rated excellent.

Polypropylene - A thermoplastic similar to polyethylene but stiffer and having a higher softening point (temperature). This material is primarily used as an insulation material. Typically, it is harder than polyethylene. This makes it suitable for thin wall insulations. The dielectric constant is 2.25 for solid and 1.55 for cellular designs.

Polyurethane (PUR) - Broad class of polymers noted for good abrasion and solvent resistance. Can be in solid or cellular form. This thermoplastic material is used primarily as a cable jacket material. It has excellent oxidation, oil, and ozone resistance. Some formulations also have good flame resistance. It is a hard material with excellent abrasion resistance. It has outstanding "memory" properties, making it an ideal jacket material for retractile cords.

Polyvinyl chloride - A general purpose thermoplastic used for wire and cable insulation and jackets.

Portable Cordage - Cable with two or more twisted conductors for flexible applications. Also called flexible cord.

POTS - Plain Old Telephone Service.

Power - The amount of work per unit of time. Usually expressed in watts and equal to the formula for power in watts. (I to the second power times R).

Power Loss - The difference between the total power delivered to a circuit, cable, or device and the power delivered by that device to a load.

Power Ratio - The ratio of power appearing at the load to the input power. Expressed in dB.

PP - Polypropylene.

PPP - Point-to-Point Protocol.

Precision Video - Video coaxial cables having very tight electrical tolerances in impedance, velocity of propagation, attenuation and structural return loss. Used in high quality applications such as live broadcast in network studios and pre- or post-production facilities.

Premise Cabling - Refers to the entire cabling system used for voice, data, video and power on a user's premise. For Local Area Networks, the cabling of choice includes unshielded twisted pairs (UTP), fiber optic and coaxial cables. Of these, the UTP market is the largest, with greatest demand for cables with four pairs that meet certain standards of performance, such as Category 5 and Category 5e.

PRI - Primary Rate Interface ISDN.

Propagation Delay - Time required for a signal to pass from the input to the output of a device.

Pseudo Random NRZ - A wave form of binary signals that may be used in a computer system. It is called NRZ, Non-Return to Zero, because the voltage does not return to zero.

PSTN - Public Switched Telephone Network.

Pulse - A current or voltage which changes abruptly from one value to another and back to the original value in a finite length of time. Used to describe one particular variation in a series of wave motions.

Putup - Packaging of finished wire or cable.

PVC - Polyvinyl chloride. Sometimes referred to as vinyl. Fire resistant.

PVDF - Polyvinylidene Fluoride.


Q

Quad - A four conductor cable. Also called "star quad".


 

نوشته شده در تاریخ یکشنبه 29 بهمن 1391    | توسط: Parviz Omidi    |    | نظرات()
ارسال به ارسال به 100 درجه کلوب دات کام