telecommunication

Communication between parties at a distance from one another. Modern telecommunication systems—capable of transmitting telephone, fax, data, radio, or television signals—can transmit large volumes of information over long distances. Digital transmission is employed in order to achieve high reliability with minimal noise, or interference, and because it can transmit any signal type, digital or analog. For digital transmission, analog signals must be subjected to a process of analog-to-digital conversion; most television, radio, and voice communications are analog and must be digitized before transmission. Transmission may occur over cables, wireless radio relay systems, or via satellite links.

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United Nations agency headquartered in Geneva. Its roots can be traced to 1865, when the International Telegraph Union was established to coordinate international development of the telegraph. It acquired its present name in 1934 and became a UN specialized agency in 1947. Its activities include regulating allocation of radio frequencies, setting standards on technical and operational matters, and assisting countries in developing their own telecommunications systems.

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The high-frequency signal components are emphasized to produce a more equal modulation index for the transmitted frequency spectrum, and therefore a better signal-to-noise ratio for the entire frequency range.

The whole system of preemphasis and deemphasis is called emphasis. The frequency curve is decided by especial time constants. The cutoff frequency can be calculated from that.

Emphasis is commonly used in audio digital recording, record cutting and in FM radio transmission.

See also

• Federal Standard 1037C and MIL-STD-188.

External links

• Emphasis - Frequency response and equalization EQ - Conversion: time constant to cut-off frequency and vice versa