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Abbreviation for quasi-random signal. A signal consisting of a bit sequence that approximates a random signal. [T1.201-1989] The unframed QRS (QRSS, QRTS, QRW) for DS1 consists of a PRBS with a 20-stage shift register with a constraint that forces the "put to a one" when the next 14 bits in the sequence would be zeros. The QRS generates every combination of 20-bit words, repeats every 1,048,575 bits, and contains high density sequences, low density sequences, and sequences that change from low density to high density and vice versa. When transmitted as the payload of a DS1 signal (framed), the QRS meets the pulse density definition "a" criteria, providing a maximum of 15-sequential zeros (14 + 1 when the frame bit is a zero), but does not meet the pulse density definition "b" criteria. (ANSI Tl.403 states: 'the quasi-random signal may be transmitted without meeting these pulse density constraints.') [T1.Rpt25-1993] Contrast with pseudorandom number sequence.
- Browse Related Terms: extended superframe (ESF), Frame, frame-alignment signal, octet alignment, QRS, quasi-random signal (QRS), superframe (SF), time-division switching
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A group of four wires composed of two pairs twisted together. Note: The pairs have a fairly long length of twist and the quad a fairly short length of twist.
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A cable formed of multiples of quads, paired and separately insulated, and contained under a common jacket.
- Browse Related Terms: balancing network, building out, nonloaded twisted pair, paired cable, phantom circuit, phantom facility, Quad, quadded cable, space-division multiplexing, time-domain reflectometer (TDR), twisted pair, twisted pair cable, two-wire circuit, uniform transmission line, video pair cable
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[A] short name referring to technology that provides tamper-resistant protection to crypto-equipment. [INFOSEC-99]
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Synonym parabolic profile.
- Browse Related Terms: quadratic profile, refraction profile, service profile, service profile management, tailing, universal personal telecommunications number
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The state of being separated in phase by 90° (
/2 radians). 2. Pertaining to the phase relationship between two periodic quantities varying with the same period, that is, with the same frequency or repetition rate, when the phase difference between them is one-quarter of their period.- Browse Related Terms: amplitude keying, analog signal, analog transmission, peak-to-peak value, Quadrature
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- Quadrature modulation in which the two carriers are amplitude modulated. 2. In analog communications, the representation (i.e., transmission) of digital information by encoding bit sequences of fixed, specified length (number of bits), and representing these bit sequences as a function of (a) the amplitude of an analog carrier; or (b) a phase shift of the analog carrier with respect to the phase that represented the preceding bit sequence, and where the permissible phase shift is an integral multiple of /2 radians (90°, or one-quarter unit interval); or (c) both. Note 1: The name quadrature originates from the stipulation that a phase shift, when required, must be an integral multiple of p/2 radians, i.e., one-quarter of a cycle (unit interval, or baud). Note 2: A representative QAM table is presented below. If the baud (carrier) rate is 1200 Hz (the usual case in modems used on conventional telephone lines), this QAM scheme permits transmission of a data rate of 9600 b/s, which is the product of the baud rate and the number of permissible phase-amplitude states.
Bit Sequence
RepresentedNormalized
Carrier
AmplitudeRelative
Phase Shift
(Degrees)000 1/2 0 (0°) 001 1 0 (0°) 010 1/2 /2 (90°)011 1 /2 (90°)100 1/2 (180°) 101 1 (180°) 110 1/2 3 /2 (270°) 111 1 3 /2 (270°) Any continuous bit stream may be represented as a combination of the eight permissible bit sequences in the above table, and transmitted as such. Note 3: According to mathematical theory, there is no limit to the data rate that may be supported by, or associated with, a given baud rate in a perfectly stable, noiseless transmission environment. In practice, the governing factors are the amplitude (and consequently, phase) stability, and the amount of noise present, in both the terminal equipment and the transmission medium (carrier frequency, or communication channel) involved. Nor does the permitted relative (incremental) phase shift necessarily have to be a multiple of
/2 radians, but of course the name "quadrature" would not apply if any other minimum phase shift were specified or permitted. - Browse Related Terms: baseband signaling, carrier shift, coherent differential phase-shift keying (CDPSK), conditioned diphase modulation, mixer, Modem, preemphasis network, quadrature amplitude modulation (QAM), quasi-analog transmission, reduced carrier transmission, signal transition, signal-plus-noise-plus-distortion to noise-plus-distortion ratio, SINAD, sub-band adaptive differential pulse code modulation (SB-ADPCM)
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Modulation using two carriers out of phase by 90° and modulated by separate signals.
- Browse Related Terms: absorption modulation, amplitude intensity modulation (AIM), amplitude modulation (AM), angle modulation, baseband local area network, carrier, carrier frequency, carrier noise level, class of emission, continuously variable slope delta (CVSD) modulation, envelope, fixed-reference modulation, Frequency Modulation (FM), modulation factor, modulation index, modulation rate, modulation suppression, off-the-air, on-the-air, optical repeater, overmodulation, percentage modulation, phase deviation, phase modulation (PM), plate modulation, precombining, predetection, pulse link repeater (PLR), quadrature modulation, radio telephony, single-sideband (SSB) emission, stereophonic crosstalk, subcarrier, two-tone keying, variable slope delta modulation
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Phase-shift keying in which four different phase angles are used. Note: In QPSK, the four angles are usually out of phase by 90°. Synonyms quadriphase, quaternary phase-shift keying.
- Browse Related Terms: biphase modulation, color keying, nonsecret encryption, phase offset, phase-shift signaling, quadrature phase-shift keying (QPSK), quadriphase, quaternary phase-shift keying, radio watch shift, transit time
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Synonym quadrature phase-shift keying.
- Browse Related Terms: biphase modulation, color keying, nonsecret encryption, phase offset, phase-shift signaling, quadrature phase-shift keying (QPSK), quadriphase, quaternary phase-shift keying, radio watch shift, transit time
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In radio communication, diversity transmission and reception in which four independently fading signals are used. Note: Quadruple diversity may be accomplished through the use of space, frequency, angle, time, or polarization multiplexing, or combinations of these.
- Browse Related Terms: add/drop multiplexing, asynchronous multiplexed transmission system, Carrier System, channel bank, muldem, multiplex (MUX), multiplexer (MUX), multiplexer/demultiplexer (muldem), PCM multiplex equipment, PDH, pilot, quadruple diversity, speech-plus, supergroup, synchronous TDM, through-supergroup equipment