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Term |
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Definition |
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Off-Air |
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RF signals (typically TV) that are received by a conventional
antenna system, including VHF and UHF broadcast stations. |
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Off-Hook |
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when the handset is lifted from it's cradle it is off hook and
competes the electrical loop, thus signaling the central office that
it wishes to dial tone. |
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Off-Peak |
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periods of relatively low system demand. Usually referring to
utilities, such as electricity or Internet. |
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Ohm |
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the unit of measurement of electrical resistance. The value of
resistance though where a potential difference of one volt will
maintain a current of one ampere |
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Ohm's Law |
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voltage equals current multiplied by resistance. V = c * R c = V / R
R = V / c |
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On-Hook |
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when the phone handset is resting in its cradle and only the bell is
active - it will ring if a call comes in. |
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Open |
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a circuit is not complete or the cable / fiber is broken. Sometimes
called a fault. |
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Open Source |
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projects that are open to the public and which draw on other
projects that are freely available to the general public |
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OSI Model (Open Systems Interconnect Reference Model) |
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an internally accepted set of standards for communication between
different systems from different vendors. The model organizes the
communications process into seven categories dependent on their
relationship to the user. |
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1. Physical Layer |
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2. Data Link Layer |
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3. Network Layer |
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4. Transport Layer |
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5. Session Layer |
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6. Presentation Layer |
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7. Application Layer |
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Outlet |
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wall-mounted device for connection to various services such as
telephone, data, video, or audio |
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Over voltage |
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an increase in voltage similar to a surge but for a longer period of
time over 2.5 seconds |
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Packet |
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the fundamental unit of information carriage in all modern computer
networks |
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Packet Switching |
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the process of routing and transferring data by means of addressed
packets so that a channel is occupied during the transmission of the
packet only, and upon completion of the transmission of the channel
is made available for the transfer of other traffic. |
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Pair |
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two wires, twisted together with a reciprocal color code. |
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Pair Twist |
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the uniform twist of an insulated copper pair that helps to improve
the effects of capacitance imbalance and electromagnetic induction.
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PAN |
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Personal Area Network |
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Parallel Circuit |
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circuit interconnection where all components share a common positive
and common negative connection. |
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Parental Controls |
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refers to the ability to restrict access to content based on subject
or rating. |
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Passive |
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a circuit or device that does not produce gain or use tubes,
transistors or integrated circuits. |
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Passive Subwoofer |
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a speaker for reproducing bass frequencies that must be power red by
a separate power amplifier. Contrasted with "active" or "powered"
subwoofers that contain an integral amplifier. |
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Password |
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a string of characters that must be entered into a security system
in a home or into a computer system to gain access. |
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Patch Chord |
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the chords interconnecting terminations at the central distribution
panel or between equipment. |
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Patching |
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A means of connecting circuits via cords and connectors that can be
easily disconnected and reconnected at another point. |
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Pay-Per-View (PPV) |
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TV programming services, such as live events or pre-recorded
programs that are multicast only to those subscribers that have been
authorized by the operator, usually meaning that the subscribers
have paid for the right to view the event in advance. In order for
the subscriber to place and confirm the order, a communication
return-path is required back to the operator. |
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PBX (Private Branch exchange) |
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telephone switching center that is owned by a private business,
compared to one that is owned by the common carrier or telephone
company |
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Peer To Peer |
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a simple kind of network that sets up a conversation between two
machines without a middleman. Both carry out the same functions.
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Peripheral Component Interconnect (PCI) |
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and internal communications and expansion bus on computers. Most
Network Interface Cards are PCI compatible. |
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Peripheral Device |
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external computer devices that are attached to the computer though
an interface cable, such as CD-ROM drives, modems, and printers.
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Personal Computer Memory Card International Association (PCMCIA)
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the standard for small, credit card-sized devices, called PC cards.
Originally designed for adding memory to portable computers, the
PCMCIA standard has been expanded several times and is now suitable
for many types of devices. |
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Photocell |
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a device that produces an electric current from visible radiant
energy (light). |
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Picture-In-Picture (PIP) |
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displaying a small picture within a larger picture by scaling down
one of the images to make it smaller. Each picture requires a video
source (camera, VCR, channel selector). Consumer TV can use POP for
viewing two channels at the same time or for viewing taped video and
a channel, etc. Videoconferencing uses POP to display pictures from
video sources at each participating site on each screen at the same
time. |
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Pixel (Picture Element) |
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a digital video image is composed of individual dots called pixels
that create the image patterns and colors. |
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Plasma Display |
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a type of flat-panel display, approximately three to five inches
thick, that works by sandwiching a neon/xenon gas mixture between
two sealed glass plates with parallel electrodes deposited on their
surfaces. The plates are sealed so that the voltage pulse passes
between two electrodes, the gas breaks down and products weakly
ionized plasma that emits UV radiation. The UV radiation activates
color phosphors and visible light is emitted from each pixel. |
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Plenum |
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space above the ceiling and below the floor or roof above, used for
air distribution or ductwork placement. |
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Plug |
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a male component of a plug/ jack connector system in premises wiring
that provides the means for a user to connect communications
equipment to the communications outlet. |
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Polarity |
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describes which side of an electrical circuit is the positive and
which is the negative. |
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Poly Vinyl Chloride (PVC) |
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the material most commonly used for the insulation and jacketing of
cable. Also used to make hard, strong plastic pipe pieces and other
products. |
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PostScript |
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the page description language created and licensed by Adobe Systems
Incorporated. PostScript technology allows various computer software
packages to create pages that can be printed on any printer with
PostScript Interpreter. |
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POTS (Plain Old Telephone Service) |
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The traditional telephone at the end of a telephone line connection
to the public switched telephone network |
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Power Amplifier |
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electronic device that ingresses the power of an incoming low level
signal to accommodate the power requirements of a loudspeaker.
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Power Output |
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a measure of a power amplifier's ability, in watts, to deliver
electrical voltage and current to a speaker. |
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Power Sum |
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Preamplifier |
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the control center of an audio/video system. Source component
switching is done here, as generally has some degree of signal
amplification associated with it. |
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Premise Wiring System |
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the entire wiring system on the user's premises, especially the
supporting wiring that connects the communications outlets to the
network interface jack. |
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Premises |
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Telephony term for the space occupied by a customer or
authorized/joint user in a building (s) on continuous or contiguous
property (except railroad rights of way, etc.) not separated by a
public road or highway. |
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Pre-wire |
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the installation of wiring in a home before the drywall is installed
during new construction. |
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Private Branch Exchange (PBX) |
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a small, privately owned version of the phone company's larger
central switching office. |
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Protocol |
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a set of agreed-upon standards that define the format, order, time,
"handshaking" and error checking method for data transfer over a
network. |
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PSTN (public switched telephone network) |
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the concatenation of the world's public circuit-switched telephone
networks, in much the same way that the Internet is the
concatenation of the world's public IP-based packet-switched
networks |
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Public Hot Spot |
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a public location where people can user their laptops, PDAs, or
other wireless devices to access the Internet or other network
services via Wi-Fi technologies. |
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Public Switched Telephone Network (PTSN) |
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the switched telephone network that carries long distance calls and
point-to-point network communications. |
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Pulling Tension |
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the amount of pull (foot-pounds of tension) placed on a cable during
installation. |
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Punch Block |
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A type of terminal strip used to connect telephone or data lines to
each other. Also called "punch-down block," "quick-connect block,"
"terminating block" and "connecting block," punch blocks use
"insulation displacement connectors" (IDCs), which cut through the
insulation as the wire is pushed into them. |
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Punch Down |
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a method for securing wire to a quick clip in which the insulated
wire is placed in the terminal groove and pushed down with the
special tool. As the wire is seated, the terminal displaces the wire
insulation to make an electrical connection. The punch down
operation may also be called trip the wire as it terminates. Also
called cut down. Usually used for telephone wiring. |
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Quality of Service (QOS) |
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a networking term that specifies a guaranteed throughput level.
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R.E.N. |
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Ringer Equivalence Number (REN) is the limit set by a Service
Provider for the total number of telephones that may be connected
simultaneously to a standard wired telephone line. |
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Radiation |
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RF energy that is emitted or leaks from a distribution system and
travels though space. These signals often cause interference with
other communication services. |
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Radio Frequency (RF) |
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refers to alternating current having characteristics such that, if
the current is input to an antenna, an electromagnetic (EM) field is
generated suitable for wireless broadcasting and/or communications.
These frequencies cover a significant portion of the electromagnetic
radiation spectrum, extending from the nine kilohertz (9 kHz), the
lowest allocated wireless communications frequency (it's within the
range of human hearing), to thousands of gigahertz (GHz). |
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525-1710 kHz |
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Am Radio Broadcasting |
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49 MHz |
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Unlicensed Devices (typically garage door openers, cordless phones,
baby monitors) |
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50-54 MHz |
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Amateur Radio |
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54-108 MHz |
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TV Broadcasting |
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154-173 MHz |
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VHF Industrial / Commercial (Police, Fire, and Ambulance) |
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174-216 MHz |
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TV Broadcasting |
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218-219 MHz |
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Interactive Video and Data |
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220-222 MHz |
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Land Mobile Systems |
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310 MHz |
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Remote Control Products |
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450-470 MHz |
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UHF Industrial / Commercial |
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470-806 MHz |
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UHF TV Broadcasting |
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810-890 MHz |
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Trucking Systems and Cellular Telephone |
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902-928 MHz |
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Unlicensed Devices (Part 15 of the FCC's Rules): 900 MHz used to be
designated for utility DA systems, but expired in 1992 and was not
reassigned due to under-use. |
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928-960 MHz |
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Multiple Address and Point-to-Point Data Communications; Microwave
Frequency band is from 953-959 MHz |
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1.8-2 GHz |
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Personal Communication Services |
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2.31-2.36 GHz |
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Satellite Digital Audio Radio |
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2.4-2.483 GHz |
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Unlicensed Devices |
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Radio Frequency Interference (RFI) |
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electromagnetic radiation which is emitted by electrical circuits
carrying rapidly changing signals, as a by-product of their normal
operation, and which causes unwanted signals (interference or noise)
to be induced in other circuits. This interrupts, obstructs, or
otherwise degrades or limits the effective performance of those
other circuits |
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Random Access Memory (RAM) |
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a type of computer memory that can be accessed randomly; that is,
any byte of memory can be accessed without touching the preceding
bytes. RAM is the primary memory used by a computer for storing
short-term data while processing. All data is lost when the power is
removed. |
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Raster |
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the series of scan lines that make up a TV picture or a computer's
display. The term "raster line" is the same as "scan line". All of
the scan lines that make up a frame of video form a raster; lines
and rows of dots such as those on the illuminated face of a video
screen. It is a matrix of pixels or the scan lines on a CRT. |
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RBOC (Regional Bell operating companies ) |
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the result of the United States antitrust action against AT&T in
1983. |
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Read Only Memory (ROM) |
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computer memory where data has been prerecorded. Once data has been
written onto a ROM chip, it cannot be removed and can only be read.
ROM retains its contents even when the computer is t turned off.
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Rear Projector |
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a type of viewing device with a translucent pane of glass or acrylic
with a customized coating and structure to optimally refract video
and computer imagery projected onto the side farthest from the
audience. |
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Receiver |
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component used in home theater and stereo applications. A decoder,
audio/ video switcher, AM/FM tuner, and an amplifier built into one
unit. The part of a communications system that converts electrical
signals into visible or audible form. |
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Red, Green, Blue (RGB) |
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the chroma information in a video signal. The basic components of a
color television system. They are also the primary colors of light
in the additive color process. |
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Redacted Instruction Set Computer (RISC) |
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a method of computer processor design where the processor uses
several small, simple operations to break down a complex
calculation. RISC excels at small instructions. |
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Redundancy |
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planning for future needs or problems by running extra cables during
the rough-in phase. |
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Reflector Lamp (R-Lamp) |
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an incandescent filament or electric discharge lamp where the sides
of the outer blown-glass bulb are coated with a reflecting material
so as to direct the light. The light-transmitting region may be
clear, frosted, or patterned. |
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Refresh Rate |
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the rate at which the picture redraws itself in one second. Usually
expressed in hertz (Hz). |
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Regional Bell Operating Company (RBOC) |
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seven RBOCs exist, each owns two or more Bell Operating Companies
(BOCs). The RBOCs were carved out of the old AT&T/Bell System during
the divestiture of the Bell operating companies from AT&T in 1984
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Registered Jack (RJ) |
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telephone and data jacks/ applications registered with the FCC.
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Remote Alarm |
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an alarm signal that is transmitted to a remote central monitoring
station. |
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Repeaters |
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a device that amplifies and regenerates signals so they can travel
further. |
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Residential Gateway (RG) |
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a devices that allows consumer premise equipment connected to
in-home networks to access and use services from any external
network regardless of media. |
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Resistance |
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the opposition to the current caused by the nature and physical
dimension of a conductor. Expressed in ohms. |
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Resolution |
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the density of lines or dots for a given area that make up an image.
Resolution determines the detail and quality in the image. A measure
of the ability of a camera or video system to reproduce detail, or
the amount of detail that can be seen in an image. A sharp, clear
picture has high resolution. |
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Return Loss |
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noise or interference caused by impedance discontinues along the
transmission line at various frequencies. Expressed in decibels.
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Return Path |
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the communications connection carrying signaling from the
subscriber, back to the operator. A return path is required for true
interactive television, and, for on-demand services such as
pay-per-view programming, VOD, and games. |
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RG59 Cable |
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a coaxial cable used for broadband video applications with a 22
gauge center conductor. Uses standard "F" connectors for video
equipment connections. |
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RG-6 |
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low loss at high frequency for satellite television and cable modem
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RG6 Cable |
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a coaxial cable used for broadband video applications with a 20
gauge center conductor, allowing a higher bandwidth then RG59 cable.
Uses standard "F" connectors for video equipment connections.
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Ring / Tip |
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The transmit and receive wires on a telephone. |
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Ring topology |
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A network topology in which every node has exactly two branches
connected to it. These nodes and branches form a ring. If one of the
nodes on the ring fails than the ring is broken and cannot work. A
dual ring topology has four branches connected to it, and is more
resistant to failures. |
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RJ |
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general term for electrical connector designs registered with the US
Federal Communications Commission |
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RJ11 |
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a communications jack with four wire connection most commonly used
for telephones, modems and fax machines. |
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RJ31 |
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a special telephone jack used to allow equipment (typically security
systems) to seize immediate control of the phone line even if that
phone line was in use. |
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RJ45 |
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a communications jack were eight wire connection most commonly used
to connect computers and other devices to a local area network
(LAN). RJ-45 connectors look similar to RJ11 connectors used for
connecting telephone equipment but that are somewhat wider. |
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Rough-In |
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the phase of a project where the boxes, cables, and in-wall
connections are installed, before the drywall is installed. |
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Router |
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a device that directs data traffic among different networks. Routers
have software that understand a wide number of protocols and can
make complex decisions. |
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