| P&L | Profit and Loss |
| P1dB | 1dB Compression Point, A figure-of-merit for output power |
| P2MP | Point to Multipoint |
| P2P | Point to Point |
| PA | Power Amplifier |
| PABX | Private Automatic Branch Exchange |
| PACA | Priority Access Channel Assignment |
| PACS | Picture Archiving Communications System |
| PAD | Program Associated Data |
| PAE | Power Added Efficiency |
| PAL | Phase Alternate Line |
| PAM | Presence and Availability Management [Forum} OR Pulse Amplitude Modulation |
| PAMS | Perceptual Analysis Measurement System |
| PAN | Personal Area Network |
| PANS | Pretty Amazing New Services |
| PAPR | Peak to Average Power Ratio |
| PAR | Peak-to-Average Ratio |
| PAR | Peak-to-Average Power Ratio |
| PARC | Per Antenna Rate Control |
| PB | Private Branch Exchange |
| PBN | Point-To-Point-Based Network OR Policy-Based Networking |
| PBX | Private Branch Exchange |
| PC | Personal Computer |
| PCB | Printed Circuit Board |
| PCDE | Peak Code Domain Error |
| PCF | Physical Control Field |
| PCI | Peripheral Component Interconnect |
| PCM | Pulse Code Modulation |
| PCM | Phase Change Materials |
| PCMCIA | Personal Computer Memory Card Interface Association – now referred to as PC card |
| PCN | Personal Communications Network |
| PCR | Program Clock Reference OR Peak Cell Rate |
| PCS | Personal Communications Systems |
| PCU | Packet Control Unit |
| PDA | Personal Digital Assistant |
| PDC | Personal Digital Cellular |
| PDD | Post-Dial Delay |
| PDE | Position Determination Equipment |
| PDG | Packet Data Gateway |
| PDH | Plesiochronous Digital Hierarchy |
| PDL | Polarization Dependent Loss |
| PDN | Public Data Network |
| PDP | Policy Decision Point |
| PDSN | Packet Data Serving Node |
| PDU | Protocol Data Unit |
| PE | Provider Edge |
| PECL | Positive Emitter-Coupled Logic |
| PEQ | Perceptual Evaluation of Speech Quality |
| PERL | Practical Extraction and Report Language |
| PESQ | Perceptual Evaluation of Speech Quality |
| PFD | Phase-Frequency Detector |
| PGA | Pin Grid Array |
| PHB | Per-Hop Behavior |
| PHEMT | Pseudomorphic High-Electronmobility Transistor |
| PHP | Personal Home Page |
| PHS | Personal Handyphone System |
| PHY | Physical Layer |
| PIC | Point-In-Call OR Predesignated Interexchange Carrier Or Primary Interexchange Carrier |
| PICMG | PCi Industrial Computer Manufacturers Group |
| PICS | Plug-In Inventory Control Systems |
| PIM | Personal Information Management OR Protocol-Independent Multicast |
| PIN | Personal Identification Number |
| PINT | PSTN and Internet Networking [IETF working group] |
| PINTG | PINT Gateway |
| PKI | Public Key Infrastructure |
| PKM | Personal Knowledge Management |
| PLA | Performance-Level Agreement |
| PLC | Planar Lightwave Circuit OR Product Life Cycle |
| PLCP | Physical Layer Convergence Protocol |
| PLD | Programmable logic device |
| PLL | Phase-Locked Loop |
| PLLs | Phase Locked Loop Frequency Syntheaizers |
| PLMN | Public Land Mobile Network |
| PLOA | Protocol Layers Over ATM |
| PLT | Power Line Telecommunication |
| PM | Performance Monitoring |
| PMD | Physical-Medium Dependent OR Polarization Mode Dispersion |
| PMDC | Polarization Mode Dispersion Compensator |
| PMI | Process Manufacturability Index |
| PMO | Present Method of Operation |
| PMP | Point-To-Multipoint |
| PMR | Professional Mobile Radio |
| PN | Personal Number |
| PNNI | Private Network-To-Network Interface |
| PnP | Plug and Play |
| PO | Purchase Order |
| PoC | Push-to-Talk Over Cellular |
| POD | Probability of Detection |
| PODP | Public Office Dialing Plan |
| POET | Partially Overlapped Echo-Cancelled Transmission |
| POF | Plastic Optic Fiber |
| POH | Path Overhead |
| POIS | Packet Optical Interworking System |
| PON | Passive Optical Network |
| POP | Short for Population |
| POP | Point of Presence |
| POP3 | Post Office Protocol 3 |
| POPS | Persons of Population |
| POS | Packet Over SONET OR Point Of Service |
| PosReQ | Position Request |
| POT | Point Of Termination |
| POTS | Plain Old Telephone Service |
| PP | Point-to-Point |
| PPD | Partial Packet Discard |
| PPM | Parts per Million |
| PPP | Point-to-Point Protocol |
| PPPoA | Point-to-Point Protocol over ATM |
| PPPoE | Point-to-Point Protocol over Ethernet |
| PPTP | Point-to-Point Tunneling Protocol |
| PP-WDM | Point-to-Point-Wavelength Division Multiplexing |
| PQ | Priority Queuing |
| PQFN | Power Quad Flat No Lead |
| PRD | Primary Reference Souce |
| PRI | Primary Rate Interface |
| PS | Picosecond |
| PSAP | Public-Safety Answering Point |
| PSC | Public Service Commission |
| PSD | Power Spectral Density |
| PSDN | Public Switched Data Network |
| PSID | Private System Identifier |
| PSK | Phase Shift Keying |
| PSN | Public Switched Network |
| PSPDN | Packet-Switched Public Data Network |
| PSQM | Perceived-Speech Quality Measurement |
| PSR | Perimeter Surveillance Radar |
| PSRAM | Pseudo-Static Random Access Memory |
| PSRS | Perimeter Security Radar System |
| PSS | Predictive Safety Systems |
| PSTN | Public Switched Telephone Network |
| PTE | Path Terminating Equipment |
| PTFE | PolyTetraFluoroEthylene |
| PTN | Personal Telecommunications Number Service |
| PTP | Point-To-Point |
| PTT | Post Telephone and Telegraph Administration |
| PUC | Public Utility Commission |
| pv-bands | Process variability bands |
| PVC | Permanent Virtual Circuit |
| PVM | Parallel Virtual Machine |
| PVN | Private Virtual Network |
| PVT | Process/Voltage/Temperature |
| PWB | Printed Wiring Board |
| PWE3 | Pseudo Wire Emulation Edge to Edge |
| PWS | Planning Workstation |
| PXC | Photonic Cross-Connect |
| PXI | PCI Extension for Instrumentation |