he packets are then reassembled into the original message at the receiving end. PacketCable PacketCable A CableLabs initiative that defines standards for the cable TV industry. It devel- ops interoperable interface specifications for two-way cable networks in order to deliver advanced real-time multimedia services. PacketCable interconnects three networks: the HFC access network, the PSTN, and IP networks. Known internationally as IP Cablecom. packet-switched network A network that consists of a series of interconnected switches that route individual packets of data over one of several redundant routes. Packet-switched net- works include X.25, Frame Relay, IP, ATM, and MPLS. PAD (packet assembler/disassembler) A protocol conversion device that accepts charac- ters in a serial data stream and converts them into packets to send across a packet-switched net- work, such as an IP network. PAL (Phase Alternating Line) The color television broadcasting system developed in West Germany and the United Kingdom that uses 625 picture lines and a 50Hz field frequency. See also NTSC and SECAM. PAM (pulse amplitude modulation) A form of modulation in which the amplitude of the pulse carrier is varied in accordance with successive samples of the modulating signal. PAN (personal area network) A network that surrounds an individual and provides net- working between badge-based computers and other input/output devices. PAP (Password Authentication Protocol) A protocol that uses a two-way handshake for the peer to establish its identity upon link establishment. The peer repeatedly sends the pass- word to the authenticator until verification is acknowledged or the connection is terminated. parallel transmission The simultaneous transmission of all the bits making up a character or byte, either over separate channels or on different carrier frequencies on the same channel. parity The state of being even numbered or odd numbered. A parity bit is a binary digit appended to a group of binary digits to make the sum of the digits either al