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.