cy. 62/14 Glossary Private Automatic Branch Exchange. (PBX in which Passive Optical Network. (Technology for imple- automatic connection is made between extensions.) menting fibre optic cable access in the local loop.) Packet Assembler/Disassembler. (Protocol conver- Point Of Presence. (In the US it refers to the point of ter used to provide access into the packet switched change over of responsibility from the local tele- network.) phone company, within a LATA, to the long distance Pulse Alteration by Line. (Television encoding sys- or inter-LATA carrier.) tem.) POPSAT Precise Orbit Positioning Satellite. Pulse Amplitude Modulation. (An analogue modu- Pacific Ocean Region. lation technique.) Promoting conference for OSI. (Japan and Far East Public Access Mobile Radio. users' group active in functional standards and inter- Peculiar And Novel Services. (Often used in con- connection testing.) junction with POTS.) Private Off-Site Paging. Private Branch Exchange. (This is often used sy- Plain Old Telephone Service. (A term loosely ap- nonymously with PABX.) plied to an ordinary voice telephone service.) Personnel Computer. Phase Locked Loop. (Component used in frequency Private Circuit. stability systems such as demodulators for fre- Pulse Code Modulation. (Transmission technique quency modulation.) for digital signals.) Pulse Phase Modulation. (An analogue modulation Personal Communications Networks. technique. Sometimes called Pulse Position Modu- Personal Communications Service. (North Ameri- lation.) can term for the service provided over a PCN.) Primary Rate Access. (ISDN, 30B+D or 23B+D Plesiochronous Digital Hierarchy. (Plesiochronous code.) transmission standard.) Pseudo Random Binary Sequence. (Signal used for Pulse Duration Modulation. (Signal modulation telecommunication system testing.) technique, also known as Pulse Width Modulation or Pulse Repetition Frequency. (Of a pulse train.) PWM.) Phase Reversal Keying. (A modification to the PSK Protocol Data Unit. (Data and control information modulation tech