- Отрасли: Telecommunications
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In an antenna radiation pattern, a zone in which the effective radiated power is at a minimum relative to the maximum effective radiated power of the main beam. Note 1: A null often has a narrow directivity angle compared to that of the main beam. Thus, the null is useful for several purposes, such as radio navigation and suppression of interfering signals in a given direction. Note 2: Because there is reciprocity between the transmitting and receiving characteristics of an antenna, there will be corresponding nulls for both the transmitting and receiving functions. 2. A dummy letter, letter symbol, or code group inserted in an encrypted message to delay or prevent its solution, or to complete encrypted groups for transmission or transmission security purposes. 3. In database management systems, a special value assigned to a row or a column indicating either unknown values or inapplicable usage. 4. Synonym node.
Industry:Telecommunications
In an analog-to-digital converter, the condition in which the input signal amplitude has just reached the threshold at which clipping begins to occur.
Industry:Telecommunications
In an amplitude-modulated facsimile system, transmission in which the maximum transmitted power corresponds to the minimum density, i.e., the white area, of the object. 2. In a frequency-modulated facsimile system, transmission in which the lowest transmitted frequency corresponds to the minimum density i.e., the white area, of the object.
Industry:Telecommunications
In an adaptive or manually operated high-frequency (HF) radio network, the automatic or manual exchange of information concerning routes to stations that are not directly reachable by the exchange originator. Note: The purpose of the exchange is to identify indirect paths and/or possible relay stations to those stations that are not directly reachable.
Industry:Telecommunications
In an adaptive high-frequency (HF) radio network, an automated process allowing the transfer of a message from message injection to addressee reception, without human intervention. Note: Through the use of machine-addressable transport guidance information, i.e., the message header, the message is automatically routed through an on-line direct connection through single or multiple transmission media.
Industry:Telecommunications
In amplitude modulation, the ratio of the peak variation actually used, to the maximum design variation in a given type of modulation. Note: In conventional amplitude modulation, the maximum design variation is considered that for which the instantaneous amplitude of the modulated signal reaches zero. When zero is reached, the modulation is considered 100%.
Industry:Telecommunications
In amplitude modulation (AM,) a band of frequencies higher than or lower than the carrier frequency, containing energy as a result of the modulation process. Note: Amplitude modulation results in two sidebands. The frequencies above the carrier frequency constitute what is referred to as the "upper sideband"; those below the carrier frequency, constitute the "lower sideband. " In conventional AM transmission, both sidebands are present. Transmission in which one sideband is removed is called "single-sideband transmission. "
Industry:Telecommunications
In alternating-current power transmission and distribution, the product of the rms voltage and amperage. Note 1: When the applied voltage and the current are in phase with one another, the apparent power is equal to the effective power, i.e., the real power delivered to or consumed by the load. If the current lags or leads the applied voltage, the apparent power is greater than the effective power. Note 2: Only effective power, i.e., the real power delivered to or consumed by the load, is expressed in watts. Apparent power is properly expressed only in volt-amperes, never watts. See diagram under effective power.
Industry:Telecommunications
In alternating-current power transmission and distribution, the product of the rms voltage and amperage, i.e., the apparent power, multiplied by the sine of the phase angle between the voltage and the current. Note 1: Vars represents the power not consumed by a reactive load, i.e., when there is a phase difference between the applied voltage and the current. Note 2: Only effective power, i.e., the actual power delivered to or consumed by the load, is expressed in watts. Volt-amperes reactive is properly expressed only in volt-amperes, never watts. Note 3: To maximize transmission efficiency, vars must be minimized by balancing capacitive and inductive loads, or by the addition of an appropriate capacitive or inductive reactance to the load.
Industry:Telecommunications
In alternating-current power transmission and distribution, the product of the rms voltage and amperage, i.e., the apparent power, multiplied by the power factor, i.e., the cosine of the phase angle between the voltage and the current. Note: Only effective power, i.e., the actual power delivered to or consumed by the load, is expressed in watts. Apparent power is properly expressed only in volt-amperes, never watts. Synonym true power. See figure by clicking on the "Pict" icon below.
Industry:Telecommunications
