the term signal ( signalis = intended for it to give an indication (signum)) is an optical or acoustic indication with a certain meaning.

  1. Most frequently signals mean a danger or the request at the beginning (free travel,Signal to the attack etc.). Beyond that the term is particularly used in 2 fields of activity:
  2. in the Eisenbahnverkehr for set up describe, Eisenbahnsignale (semaphores) or light signals operated by remote control (in Switzerland also general for road signs)
  3. in physics and the cybernetics as carriers of one Information - e.g. the modulation of a carrier wave or a locally deviating effect in a field.
More a-wisely for vehicles with the operation talk ball express

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of case the signal a meaning contains, can it for transmission of a message be used. Also without a signal admitted one in a while agoMeaning contains (case 3), can carry it for information. Also of electrical, chemical or body-linguistic indications signal effect can go out - e.g. with an odoriferous substance or a “speaking gesture “.

If a signal is used for the evaluation by information, one calls it information signal. If it obstructs the transmission of information, then it is called spurious signal.

Researchers of the University of Geneva could 2004 for the first time experimentally prove that the signal speed can be larger never, as the speed of light in the vacuum (299 792.5 km/s). This applies, although thoseso-called group velocity, i.e. the propagation speed of the light pulses in an optical waveguide cable (or another close medium), nearly the double of the speed of light to reach can (N. Gisin et al., Physical Review Letters Vol.93, kind. 203902).

special meanings

incertain fields of activity has the signal term a more special meaning:


in the traffic an indication set up for the road user at the distance, e.g. Statements about trafficability and maximum speed of a certain distance section meets. One differentiates between the following signals:

process symbol

a certain, defined, recognized form of a dynamic procedure, that as referenceon another event or another procedure serves. In particular changes in status or process. (Process symbol) as symbol expression of one however constituted communication and/or. a notification procedure within a sense system.


of measuring signals in the time intervall, usually inForm of a similar potential gradient are present, also Zeitsignale are called.


  • a short, pre-defined message to a computer program.
  • a function of a class, which does not have a function trunk and with one “slot” be connected can; Qt)
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in electro-technology the Zeitverlauf of a transferred electrical size; see Zeitsignal and in the television and video technology the television signal.


in military affairs one uses signals, around friendly or hostile troops information comes tooleave; see Schamade, Flaggensignal.

social sciences

a political signal is an action, of whose model - and other effect or of them culturally implied meanings an influence of the participants of a political system one expects.

In addition political

magazine “signal” was the name of a propaganda magazine of the national socialists in the third realm, which reached and in 25 languages was published an edition of up to 2.500.000.

to security

see distress signal, warning signal

See also:

This article or section is still incomplete and exhibits the following gaps :

Breakdown into technical signals andSignals of the social interaction.
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