A null detected by listening for the minimum or the absence of an audible signal


Related Terms

CQ

The two-letter signal, to be used by flags, radiotelephony or radiotelegraphy, meaning "Calling All Ships".

DISTORTION

  1. Any undesired change in the waveform of an electric signal passing through a circuit or other transmission medium.
  2. In general, the extent to which a system fails to accurately reproduce the characteristics of an input signal at its output.
  3. Any undesired change in the waveform of a sound wave.

DEAD TIME

  1. The time interval between a change in the input signal to a process control system and the response to the signal.
  2. The time interval, after a response to one signal or event, during which a system is unable to respond to another. Also known as insensitive time.

AMPLIFICATION

  1. An increase in signal magnitude from one point to another, or the process causing this increase.
  2. Of a transducer, the scalar ratio of the signal output to the signal input

PHOTOELECTRIC DEVICE

A device which gives an electrical signal in response to visible, infrared, or ultraviolet radiation.

PHASE-COMPARISON RELAYING

A method of detecting faults in an electric power system in which signals are transmitted from each of two terminals every half cycle so that a continuous signal is received at an intermediate point if there is no fault between the terminals, while a periodic signal is received if there is a fault.

PERMISSIVE STOP

A railway signal indicating the train must stop but can proceed slowly and cautiously after a specified interval, usually 1 minute.

PARASITIC

An undesired and energywasting signal current, capacitance, or other parameter of an electronic circuit.

OVERLOAD LEVEL DEVICE

tion ceases to be satisfactory as a result of signal its original level. grade separation.

OUTPUTMETER

Analternating-currentvoltmeter connected to the output of a receiver or amplifier to measure output signal strength in volume units or decibels.

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