Abbreviation for quality assurance.

Abbreviation for quadrature amplitude modulation.

Abbreviation for quality control.

QoS Class Identifier

Abbreviation for quarter common intermediate format.

Quality of Experience

Quality of Service

Quality of Service Management

Abbreviation for quadrature phase-shift keying.

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… (Read More →)

Abbreviation for quasi-random signal source.

Abbreviation for quasi-random test signal.

Abbreviation for quasi-random word.

Quality of Service Specification

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.

A cable formed of multiples of quads, paired and separately insulated, and contained under a common jacket.

[A] short name referring to technology that provides tamper-resistant protection to crypto-equipment. [INFOSEC-99]

Synonym parabolic profile.

1. 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.

1. 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… (Read More →)

Modulation using two carriers out of phase by 90° and modulated by separate signals.

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.

Synonym quadrature phase-shift keying.

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.

A single-mode optical fiber that has four claddings.
Note 1: Each cladding has a refractive index lower than that of the core. With respect to one another, their relative refractive indices are, in order of distance from the core, lowest, highest, lower, higher.
Note 2: A quadruply clad fiber has the advantage of very low macrobending losses. It also has… (Read More →)

One who has demonstrated skills and knowledge and is trained to work with powered communication circuits, shall have access to live parts and has received safety training to identify the hazards and reduce the associated risk.

1. All actions taken to ensure that standards and procedures are adhered to and that delivered products or services meet performance requirements.
2. The planned systematic activities necessary to ensure that a component, module, or system conforms to established technical requirements.
3. The policy, procedures, and systematic actions established in an enterprise for the purpose of providing and maintaining a… (Read More →)

A management function whereby control of the quality of (a) raw materials, assemblies, produced materiel, and components, (b) services related to production, and (c) management, production, and inspection processes is exercised for the purpose of preventing undetected production of defective materiel or the rendering of faulty services.

In a reactive circuit, the ratio of the reactance in ohms divided by the resistance in ohms.

The overall acceptability of an application or service, as perceived subjectively by the end-user. Quality of Experience includes the complete end-to-end system effects (client, terminal, network, services infrastructure, etc). Overall acceptability may be influenced by user expectations and context.

1. The performance specification of a communications channel or system.
Note: QOS may be quantitatively indicated by channel or system performance parameters, such as signal-to-noise ratio (S/N), bit error ratio (BER), message throughput rate, and call blocking probability.
2. A subjective rating of telephone communications quality in which listeners judge transmissions by qualifiers, such as excellent, good, fair, poor, or… (Read More →)

A process in which the continuous range of values of an analog signal is sampled and divided into nonoverlapping (but not necessarily equal) subranges, and a discrete, unique value is assigned to each subrange.
Note: An application of quantization is its use in pulse-code modulation. If the sampled signal value falls within a given subrange, the sample is assigned the… (Read More →)

Synonym quantizing distortion.

In the quantization process, the discrete value assigned to a particular subrange of the analog signal being quantized.

Synonym quantizing noise.

In a digital feedback loop, the digital signal that is fed back.
Note 1: Several forms of analog-to-digital converters contain a quantized feedback loop following the basic A-D converter.
Note 2: The feedback signal is often processed before introducing it to the loop.

Distortion that results from the quantization process. Synonym quantization error.

In digital transmission, the number of discrete signal levels transmitted as the result of signal digitization.

Noise caused by the error of approximation in quantization.
Note: Quantizing noise is dependent on the particular quantization process used and the statistical characteristics of the quantized signal. Synonym quantization noise.

In an optical source or detector, the ratio of the number of output quanta to the number of input quanta.
Note: Input and output quanta need not both be photons.

Noise attributable to the discrete and probabilistic nature of physical phenomena and their interactions.
Note 1: Quantum noise represents the fundamental limit of the achievable signal-to-noise ratio of an optical communication system. This limit is never achieved in practice. [After FAA]
Note 2: Examples of quantum noise are photon noise in an optical signal and shot noise in an electrical… (Read More →)

Synonym quantum-noise-limited operation.

Operation wherein the minimum detectable signal is limited by quantum noise. Synonym quantum-limited operation.

A video format defined in ITU-T Recommendation H.261 that is characterized by 176 luminance pixels on each of 144 lines, with half as many chrominance pixels in each direction.
Note: QCIF has one-fourth as many pixels as the full common intermediate format.

A clock containing a quartz oscillator that determines the accuracy and precision of the clock.

An oscillator in which a quartz crystal is used to stabilize the frequency.
Note: The piezoelectric property of the quartz crystal results in a nearly constant output frequency, which is dependent upon the crystal size, shape, and excitation.

A digital signal that has been converted to a form suitable for transmission over a specified analog channel.
Note: The specification of the analog channel should include frequency range, bandwidth, signal-to-noise ratio, and envelope delay distortion. When quasi-analog form of signaling is used to convey message traffic over dial-up telephone systems, it is often referred to as voice-data. A modem… (Read More →)

Transmission in which a special-purpose modulator is used to convert digital signals into an analog form suitable for transmission over an analog voice-grade circuit.
Note: A complementary demodulator is used to recover the digital signal at the other end of the circuit. See modem.

A limited case of the nonassociated mode of signaling in which the path taken by a message through the signaling network is predetermined and fixed at a given point in time. [T1.226-1992]

In video and multimedia applications, the bit-rate reduction of an image signal, by an algorithm that recognizes the high degree of correlation ascertainable in specific images.
Note 1: The final image does not replicate the original when viewed in direct comparison, but the losses are designed to be unrecognizable under the intended display conditions.
Note 2: The algorithm may often… (Read More →)

See QRS.

Synonym quadrature phase-shift keying.

A digital signal having four significant conditions.

Any operation which obtains either data or attributes from an object [POSIX.6].

In adaptive high-frequency (HF) radio, an automatic-link-establishment (ALE) call that requests responses from stations having connectivity to the destination specified in the call.

A set of items, such as telephone calls or packets, arranged in sequence.
Note: Queues are used to store events occurring at random times and to service them according to a prescribed discipline that may be fixed or adaptive.

1. A series of outgoing or incoming calls waiting for service.
2. In a store-and-forward switching center, the outgoing messages awaiting transmission at the outgoing line position.

The process of entering elements into or removing elements from a queue.

1. In a switched network, the time between the completion of signaling by the call originator and the arrival of a ringing signal at the call receiver.
Note: Queues may be caused by delays at the originating switch, intermediate switches, or the call receiver servicing switch.
2. In a data network, the sum of the delays between the request for… (Read More →)

The theoretical study of waiting lines, expressed in mathematical terms--including components such as number of waiting lines, number of servers, average wait time, number of queues or lines, and probabilities of queue times' either increasing or decreasing.
Note: Queuing theory is directly applicable to network telecommunications, server queuing, mainframe computer queuing of telecommunications terminals, and advanced telecommunications systems.

With respect to the rf spectrum, an area in which emissions are restricted for the purpose of minimizing possible impact on the operations of radio astronomy or other activities that are highly sensitive to rf interference.

In an FM receiver, the phenomenon that results in less noise when an unmodulated carrier is present than when there is no carrier present.
Note: Quieting is expressed in dB.

1. In a digital video system, a sampling structure where the luminance and color-difference samples are generated from pixels arranged on one of two congruent rectilinear grids.
Note: One grid is displaced horizontally from the other by half the horizontal pixel spacing. The alternate grid is usually chosen for alternate lines, but may also be chosen for alternate field/frames. [After… (Read More →)