An exchange carrier (EC) service that is provided by suitably equipped end-office switching systems, and by means of which are provided carrier identification codes for calling users' calls outside the access service area when they are dialed without a customer accounting code (CAC). [After T1.104-199]

Referring to that portion of the circuitry of a receiver which, with respect to the signal being processed, is chronologically prior to the detection.
Note: Predetection signals contain the carrier signal and all modulation, and are basically at radio frequencies.

Synonym maximal-ratio combiner.

A system process designed to increase, within a band of frequencies, the magnitude of some (usually higher) frequencies with respect to the magnitude of other (usually lower) frequencies, in order to improve the overall signal-to-noise ratio by minimizing the adverse effects of such phenomena as attenuation differences, or saturation of recording media, in subsequent parts of the system.
Note: Preemphasis… (Read More →)

In FM broadcasting, the improvement in the signal-to-noise ratio of the high-frequency portion of the baseband, i.e., modulating, signal, which improvement results from passing the modulating signal through a preemphasis network.
Note: Preemphasis increases the magnitude of the higher signal frequencies, thereby improving the signal-to-noise ratio. At the output of the discriminator in the FM receiver, a deemphasis network restores… (Read More →)

A network inserted in a system in order to increase the magnitude of one range of frequencies with respect to another.
Note: Preemphasis is usually employed in FM or phase modulation transmitters to equalize the modulating signal drive power in terms of deviation ratio. The receiver demodulation process includes a reciprocal network, called a deemphasis network, to restore the original… (Read More →)

See multilevel precedence and preemption.

The seizure, usually automatic, of military system facilities that are being used to serve a lower precedence call in order to serve immediately a higher precedence call.

In military telephone systems, a distinctive tone that is used to indicate to connected users, i.e., subscribers, that their call has been preempted by a call of higher precedence.
Note: An example of preemption tone is a distinctive, steady, high-pitch tone transmitted for three seconds or until the preempted user hangs up. [From Weik '89]

[In telephone communications,] an indicator consisting of one or more digits, that allows the selection of different types of number formats (e.g., local, national or international), transit networks and/or the service.
Note 1: Prefixes are not part of the number and are not signaled over internetwork and international boundaries.
Note 2: When prefixes are used, they are always entered by… (Read More →)