Glossary P-Q0-A | B | C-Cn | Co-Cz | D | E | F-G | H-I | J-L | M | N-O | P-Q | R | S | T | U-Z
0-A | B | C-Cn | Co-Cz | D | E | F-G | H-I | J-L | M | N-O | P-Q | R | S | T | U-Z
- Packet: A group of
bits(including data & call control signals) transmitted as a whole on a
packet-switching network. Usually smaller than a transmission block.
- Packet Assembler/Disassembler: (PAD) A device for
connecting a terminal or computer to an X.25 network.
- Packet Data Network: (PDN) Often used to mean
- Packet Switching: A wide area communications
technique in which data is packeted for transmission over a shared data network
rather than over dedicated lines. Packet switching differs from circuit
switching in that is uses virtual circuits, i.e. it is made up of bandwidth
allocated on demand from a network of shared circuits.
- PAD: See Packet Assembler/Disassembler
- PAP: See Printer Access Protocol
- 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
- Parallel Extender: A kit that
usually contains a Transmitter, Receiver, and a small wire to connect the two
for connecting a parallel port on a computer to a parallel
- Parallel Processing: Concurrent or simultaneous execution of
two or more processes, or programs within the same processor, as contrasted
with serial or sequential processing.
- Parallel Transmission:
Transmission mode that sends a number of bits simultaneously over separate
lines (example, 8 bits over 8 lines). Usually unidirectional.
Bit: A check bit added to a character to make the total number of 1's in
the character an even or odd number.
- Parity Checking: The process of
checking that a received character has the correct parity bit. Both the sending
& the receiving DTE's must be set to operate for the same parity indicates an
error & may cause an appropriate remedial action to be initiated.
Through: Describing the ability to gain access to one network element
- Patch Cable: A cable with plugs or terminals on each
end of the conductors to temporarily connect circuits of equipment
- Patch Cord: A length of cable with connectors on one or
both ends used to join telecommunications circuits at the
- Patch Panel: A system of terminal blocks, patch cords
& backboards that facilitates administration of cross- connect fields for moves
- PBX: See Private Branch
- PCC: See Premises Communication
- PCF: See Physical Control
- PDN: See Packet Data
- PE: See Polyethylene
The maximum instantaneous value of a varying current or
- Peer-to-Peer: A system in which two or more nodes or
processes can initiate communications with each other. Usually describes a
network in which all nodes have the ability to share resources with other nodes
so that a dedicated server can be implemented but is not
- Performance Management: Measures & records resource
utilization. It is one of the categories of network management defined by the
- Phase: An angular relationship between waves.
Modulation: A modulation technique. The phase of the carrier sine wave is
modified to add the information.
- Phase Shift: A change in the phase
relationship between two alternating quantities.
(Receiver) Transforms light into electricity. The silicon photo diode is most
commonly used for relatively fast speeds & good sensitivity in the 0.75 um to
0.95 um wavelength region. Avalance photodiodes (ADP) combine the detection of
optical signals with internal amplification of photo-current. Internal gain is
realized through avalance multiplication of carriers in the junction region.
The advantage in using an ADP is its higher signal-to-noise ratio, especially
at high bit rates. Physical Address: The MAC-layer address of a node, as
opposed to the software-defined network-layer address.
- Physical Control Fields: (PCF) The Access Control & the
Frame Control bytes in a Token Ring header.
- Physical Layer: The
lowest level of the OSI reference model. The Physical layer specifies the
physical transmission media, signaling levels, connectors, & related interface
- Pickup: Any device which is capable of transforming a
measurable quantity of intelligence (such as sound) into relative electrical
- Pico: Prefix meaning one-millionth of one-millionth
- Picofarad: one millionth of a farad
Wire: Fine stranded, extra flexible, rope lay lead wire attached to a
shield for terminating purposes.
- Pin Configuration: A predetermined
relationship between the terminals in a connector & the conductors in a cable
that specifies the terminals to which each conductor is to be
- Ping: Network management software used to test if a
managed device is reachable. The ICMP packets used for this function are called
echo packets or "pings."
- Pinouts: Pin configurations for
- Pipe: A device that acts as an interface or buffer between
applications & devices.
- Pitch: In flat cable, the normal distance
between the index edges of two adjacent conductors.
- Pixel: Picture
element; smallest unit of a graphics or video display; light characteristics
(color & intensity) which can be coded into an electrical signal for
- Plastic: High polymeric substances, including both
natural & synthetic materials.
- Plenum: A space within the building
created by building components, designed for the movement of environmental air
(a space above a suspended ceiling or below an access floor).
The part of the two mating halves of a connector which is moveable when not
fastened to the other mating half.
- Point-to-Point Link: Communication
link connecting two DTE's
- Point-to-Point Protocol:
(PPP) A standard TCP/IP related protocol used to communication over a serial
point-to-point link such as T-1 trunk between routers.
- Polarity: A
condition when there are two opposing voltage levels.
- Polling: An
access method with which a hub asks each node in turn if it has data to
- Polyethylene: (PE) A type of plastic
material used to make cable jacketing. Having excellent electrical
- Polymer: A substance made of many repeating chemical
units or molecules. The term polymer is often used in place of plastic, rubber,
- Polypropylene: A thermoplastic similar to polyethylene
but stiffer & having a higher softening point
- Polyurethane: Broad class of polymers noted for good
abrasion & solvent resistance, Can be in solid or cellular form.
- Polyvinyl Chloride: (PVC) A general purpose thermoplastic
used for wire & cable insulation & jackets.
- Port: A point of exit or
entry for a data channel in a network.
- Port Number: A field in the
TCP & UDP headers that specifies which applications are sending & receiving the
messages. The port field is the layer interface that enables TCP & UDP to
transfer messages to any application.
- Potting: Sealing by filling
with a substance to exclude moisture.
- Power: The amount of work per
unit of time. Usually expressed in watts.
- PPP: See Point-to-Point Protocol
Communication Cable: (PCC) CSA (Canadian Standards Association) Cable
- Presentation Layer: Layer six of the ISO reference
model; provides standards for restructuring data into the required format,
character set, or language.
- Print Spooler: An
application that manages print requests or jobs so that one job can be
processed while other jobs are placed in a queue until the printer has finished
with preceding jobs.
- Printer Access Protocol:
(PAP) An AppleTalk protocol governing transmissions between workstations &
printers or similar devices.
- Printer Server: An intelligent device
used to transfer information to a series of printers.
- Private Branch Exchange: (PBX) A private telephone
- Processing Unit: A unit of a computer that contains the
circuits controlling the interpretation & execution of commands. It is the
heart of the computer.
- Programmable Read-Only
Memory: (PROM) A nonvolatile memory chip that stores data or programs
permanently. Compare with volatile memory.
- PROM: See Programmable Read-Only Memory
- Propagation delay: The
time required for data to travel from transmission point to
- Proprietary: A protocol or communications system
developed by a company, as opposed to those emanating from a standards
- Protected mode: CPU (Central Processing Unit) mode in
which applications must request memory allocations from the operating system, &
these allocations are then protected from other applications"
- Protective Ground: (GND) One of the signals in the DTE-DCE
interface. Protective Ground discharges harmful electrical current, thereby
protecting the equipment & users.
- Protocol: A standardized set of
rules that specify the format, timing, sequencing, and/or error checking for
- Protocol Multiplexing: A technique for
unambiguously transmitting more than one protocol over the same link. For
example both Ethernet & PPP allow protocol Multiplexing.
stack: A representation of the hierarchical nature of a protocol
- Protocol Suite: A hierarchical set of related
- Proxy: Allows the LAN to connect to the internet through
addressing. This will not allow the internet to access the Local Area Network
- PSTN: See Public Switched Telephone
- Pubic Network: A network operated by common carriers or
telecommunications administrations for the provision of circuit switched,
packet-switched, & leased-line circuits to the public.
- Public Switched Telephone Network: (PSTN) Any switching
communications system such as Telex, TWX, or public telephone networks that
provides circuit switching to many customers.
- Publishing: Making
resources available to network users.
- Pulling Eye: A device used to
pull cable into or from a duct.
- Pulse: A current or voltage which
changes abruptly from one value to another & back to the original value in a
finite length of time. Used to describe one particular variation in a series of
- Punchdown: A method for securing wire to a quick clip
in which the insulated wire is placed in the terminal groove & pushed down with
a special tool. As the wire is seated, the terminal displaces the wire
insulation to make an electrical connection. The punchdown operation may also
trim the wire as it terminates. Also called cut down.
- PVC: See Polyvinyl Chloride
- QBE: See Query By
- Query By Example: (QBE) A database
front-end that requests the user to supply an example of the type of data to be
- Query Language: A programming language that permits users
to retrieve information from a database.
- Queue: An ordered list of
items waiting to be processed.