PAD - Packet Assembler/Disassembler

PAL - Phase Alternating Line

PAP - Password Authentication Protocol

PBX - Private Branch Exchange

PC - Priority Control

PCB - Printed Circuit Board

PCM - Pulse Code Modulation

PCR - Peak Cell Rate

PCS - Personal Communications Software

PD - Propagation Delay

PDH - Plesiochronous Digital Hierarchy

PDSC - Power Distribution Servicing Cabinet

PDU - Packet Data Unit

PDU - Protocol Data Unit

PGL - Peer Group Leader (ATM Forum, PNNI)

PIA - Program Integrity Assurance (part of NECA function; review applications and invoices for compliance with program rules)

PID - Protocol IDentifier

PING - Packet INternet Groper

PIP - Picture-In-Picture

PLCP - Physical Layer Convergence Protocol

PLL - Phase Locked Loop

PM - Physical Medium

PMD - Physical Medium Dependent

PMP - Point to Multipoint

P-NNI - Private Network-to-Network Interface or Private Network Node Interface

PO - Proper Operation

POH - Path Overhead (SONET)

POI - Path Overhead Indicator

POTS - Plain Old Telephone Service

PPD - Partial Packet Discard

PPP - Point-to-Point Protocol

PRI - Primary Rate Interface

PROM - Programmable Read Only Memory

PSTN - Public Switched Telephone Network

PT - Payload Type

PTE - Path Terminating Equipment (SONET)

PTI - Payload Type Identifier

PTSE - PNNI Topology State Element (ATM Forum, PNNI)

PTSP - PNNI Topology State Packet

PTT - Post, Telephone, and Telegraph

PTZF - Pan-Tilt-Zoom-Focus

PUC - Public Utility Commission

PVC - Permanent Virtual Circuit

PVCC - Permanent Virtual Channel Connection

PwC - PricewaterhouseCoopers (contractor handling billings, collections and disbursement functions for USAC)

QA - Quality Assurance

Q-Factor - Quality for JPEG

QoS - Quality of Service