In a network, a group of users permitted to communicate with each other but not with users outside the group.
Note: A user data terminal equipment (DTE) may belong to more than one closed user group.

A closed user group in which at least one member of the group has a facility that permits communication with one or more users external to the closed user group.

An electromagnetic waveguide (a) that is tubular, usually with a circular or rectangular cross section, (b) that has electrically conducting walls, (c) that may be hollow or filled with a dielectric material, (d) that can support a large number of discrete propagating modes, though only a few may be practical, (e) in which each discrete mode defines the propagation constant… (Read More →)

The integral, over all frequencies, of the absolute value of the closed-loop transfer function of a phase-locked loop.
Note: The closed-loop noise bandwidth, when multiplied by the noise spectral density, gives the output noise power in a phase-locked loop.

In cryptography, the originator's confirmation of the integrity of the entire transaction, i.e., of both the transaction request and its transaction response. [After X9.19]

A mathematical expression (algorithm) describing the net result of the effects of a closed (feedback) loop on the input signal to the circuits enclosed by the loop.
Note 1: The closed-loop transfer function is measured at the output.
Note 2: The output signal waveform can be calculated from the closed-loop transfer function and the input signal waveform.

1. An environment in which special attention is paid (in the form of authorizations, security clearances, configuration controls, etc. ) to protect data and resources from accidental or malicious acts. [2382-pt.8]
2. [An] environment providing sufficient assurance that applications and equipment are protected against the introduction of malicious logic during an information system (IS) life cycle. Closed security is based… (Read More →)

Synonym splice closure.

In the transmission of electromagnetic signals, attenuation caused by absorption and scattering by water or ice particles in clouds.
Note: The amount of cloud attenuation depends on many factors, including (a) the density, particle size, and turbulence of the clouds and (b) the transmission path length in the clouds.

Configuration Management