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Practical_modern_SCADA_protocols_-_dnp3,_60870-5_and_Related_Systems

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Appendix A: Glossary 407<br />

Packet<br />

PAD<br />

Parallel<br />

transmission<br />

PBX<br />

PCF<br />

PCM<br />

PCMCIA<br />

PCS<br />

PDH<br />

PDU<br />

Peripherals<br />

Physical layer<br />

PLC<br />

PLL<br />

Point-to-point<br />

Polyethylene<br />

PVC<br />

A group of bits (including data <strong>and</strong> call control signals)<br />

transmitted as a whole on a packet switching network. Usually<br />

smaller than a transmission block.<br />

Packet Assembler/Disassembler. An interface between a terminal<br />

or computer <strong>and</strong> a packet switching network.<br />

The transmission method where data is sent simultaneously<br />

over separate parallel lines. Usually unidirectional such as the<br />

Centronics interface for a printer.<br />

Private Branch Exchange.<br />

Point Control Function. A polling type of medium access<br />

control used by IEEE 802.11 Wireless LANs for real-time data.<br />

Pulse Code Modulation. The sampling of a signal <strong>and</strong> encoding<br />

the amplitude of each sample into a series of uniform pulses.<br />

Personal Computer Memory Card Industries Association.<br />

St<strong>and</strong>ard interface for peripherals for laptop computers.<br />

Personal Communication Service (IS-136) based on D-AMPS<br />

(IS-54).<br />

Plesiochronous Digital Hierarchy.<br />

Protocol Data Unit.<br />

The input/output <strong>and</strong> data storage devices attached to a computer<br />

e.g. disk drives, printers, keyboards, display, communication<br />

boards, etc.<br />

Layer one of the ISO/OSI Reference Model, concerned with<br />

the electrical <strong>and</strong> mechanical specifications of the network<br />

termination equipment.<br />

(1) Programmable Logic Controller. (2) Power Line Carrier.<br />

Phase Locked Loop.<br />

A connection between only two items of equipment.<br />

A family of insulators derived from the polymerization of<br />

ethylene gas <strong>and</strong> characterized by outst<strong>and</strong>ing electrical<br />

properties, including high IR, low dielectric constant, <strong>and</strong> low<br />

dielectric loss across the frequency spectrum.<br />

Polyvinyl chloride. A general purpose family of insulation<br />

materials whose basic constituent is polyvinyl chloride or its<br />

copolymer with vinyl acetate. Plasticizers,stabilizers, pigments<br />

<strong>and</strong> fillers are added to improve mechanical <strong>and</strong>/or electrical<br />

properties of this material.

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