quad cable - A cable with four insulated, copper, nontwisted strands. Typically, the conductors are color coded red, green, black, and yellow. Also called quad.

quadrature amplitude modulation (QAM) - A means of encoding digital data that uses variations in signal amplitude and phase. QAM signals have 2z" states, where each state encodes 2N bits. The encodings most commonly used include QAM-4, QAM-16, QAM-64, and QAM-256.

quadrature phase shift keying (QPSK) - Phase-shift keying in which four different phase angles are used. In QPSK, the four angles differ in phase by 90 degrees.

quad-shielded - A cable consisting of a foil-braid-foil-braid shield.

quality of service (QoS) - 1. A commitment to performance, based on predefined service parameters. 2. A measure of the level of service provided on a network.

quarter common intermediate format (QCIF) - A videoconferencing format that specifies data rates of 30 frames per second, with each frame containing 144 lines and 176 pixels per line. This format is defined in ITU-T Recommendation H.261.

quarter common intermediate format/ quarter standard input format (QCIFI QSIF) - A videoconferencing format that specifies data rates of 30 frames per second, with each frame containing 144 lines and 176 pixels per line. QCIF support is required by the ITU H.261 videoconferencing standard. See also common intermediate format/standard input format.

quarter-wave antenna - A radio antenna that is one-fourth the size of the wavelength of the design frequency.

quartet - A grouping of 4 bits. See also nibble.

queuing - A quality of service technique that classifies data by priority and stores it in a queue prior to processing.

quote - See proposal.