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Crosstalk using the example of a tape recording: In the pause between two voices, both voices can be heard softly. The crosstalk was caused by influencing the magnetization of neighboring tape windings.

Crosstalk or crosstalk , English term crosstalk , abbreviated to XT , is a term from telephony and originally referred to an effect through which one can quietly overhear another conversation on the phone - hence the name. Today the term is generally used in communications technology for the undesirable mutual influencing of actually independent signal channels . The amount of crosstalk between channels is expressed in decibels (dB).

Electrical crosstalk

The electrical crosstalk (English crosstalk or X-talk ) is based on a simple physical process: a pair of wires represents an electrical oscillating circuit and can therefore serve as both a transmitter and a receiver of electrical fields. If an electrical signal , such as the voice signal, is now transmitted via a wire pair that is routed together with several other wire pairs in a cable, this signal is coupled to other wire pairs. The coupling takes place inductively , capacitively or galvanically , whereby the coupled signal level is only very low. One speaks of crosstalk attenuation .

In full-duplex data transfer There are two types of unwanted disturbances: near-end crosstalk and far end cross talk , see below.

Various techniques are used to reduce crosstalk: stranding and shielding of the cable cores, use of coaxial cables , use of fiber optic cables. Fiber optic cables are insensitive to crosstalk between the individual glass fibers.

With certain modulation methods, crosstalk also occurs between the individual channels in the medium (for example WDM in optical waveguides).

Near crosstalk

As near-end crosstalk or NEXT ( near end cross talk, NEXT ) refers to the interference signal , the most proximal end is, thus on side of the transmitter, is received. The level of the interference signal is greater than with the FEXT.

Senderseite                               Empfängerseite
Signal A → ========================== → Signal A - Dämpfungsverluste
             || |  |  |   :     :
             VV V  V  v   v     v
 NEXT(A) ← ========================== → FEXT(A)

Long distance crosstalk

Far end cross talk or far-end crosstalk ( far end cross talk, FEXT ) is the coupling by an interfering transmitter "at the far end from the victim receiver" or "on the side of the transmitter to be received". Interferers and victims are at different and therefore distant ends of the cable. The disturbance experiences the attenuation of the line.

Foreign crosstalk

The alien crosstalk ( Alien crosstalk, AX ) is not caused by signal coupling through the lines of a common harness, but by other nearby cables laid. This coupling occurs uncorrelated to the useful signal and is just as difficult to filter out as noise. The alien crosstalk is also subdivided into whether it is observed at the near or far end.

  • Fremdnahübersprechen ( alien near end crosstalk, ANEXT )
  • Foreign remote crosstalk ( alien far end crosstalk, AFEXT )

Symbol crosstalk

In contrast to other types of crosstalk, symbol crosstalk represents temporal crosstalk on the same channel and can occur during the transmission of digitally coded information. It is the interaction between (not necessarily directly) successive symbols in transmission technology .

Acoustic crosstalk

In audio engineering , crosstalk is also used when unwanted sound is picked up from neighboring sound sources by microphones , or when recording or transmitting with several microphones ( main microphone and support microphones ). More precisely, this is acoustic crosstalk ( leakage , spillage or bleeding ). Musical instruments speak acoustically, such as the hi-hat on the snare microphone. This "bleed" as crosstalk is not generally undesirable, but is also used for sound design when creating a space; see the three-to-one rule (3: 1 rule).

Crosstalk in consumer electronics

Electrical crosstalk also occurs in entertainment electronics devices , and this usually occurs between the two stereo channels. Amplifiers are less affected by this, the phenomenon is more pronounced with analog signal sources such as turntables , cassette decks and tape recorders . In the 1960s, crosstalk when playing records was so high that half of the instruments and voices were recorded almost exclusively on one of the channels to achieve a stereo effect ( stick stereophony ). In digital signal processing, such as in CD players or MP3 files, the phenomenon no longer occurs (or only occurs to a negligible extent).

A special type of crosstalk occurs with the copy effect , in which stronger signals on a magnetic tape are copied onto the adjacent layers of a tape reel.


  • Rudolf Elsner: Message Theory . The transmission channel, Springer Fachmedien, Wiesbaden 1977, ISBN 3-519-06104-X .
  • Alexandru Spǎtaru: Theory of Information Transfer . Signals and interference, Friedrich Vieweg & Sohn Verlagsgesellschaft, Braunschweig 1973.
  • Bob Vachon, Rick Graziani: Wide Area Networks. CCNA exploration companion guide, Addison-Wesley Verlag, Munich 2009, ISBN 978-3-8273-2750-5 .
  • Michael Dickreiter , Volker Dittel, Wolfgang Hoeg, Martin Wöhr (eds.): Manual of the recording studio technology. 8th revised and expanded edition, 2 volumes, Walter de Gruyter Verlag, Berlin / Boston 2014, ISBN 978-3-11-028978-7 .
  • Günter Kemnitz: Technical computer science . Volume 1: Electronics. Springer Verlag, Berlin / Heidelberg 2009, ISBN 978-3-540-87840-7 .
  • Jörg Rech: Ethernet . Technologies and protocols for computer networking, 3rd updated edition, Heise Zeitschriften Verlag GmbH & Co KG, Hanover 2014, ISBN 978-3-944099-04-0 .
  • Leon Lichtenstein: About crosstalk in combined telephone circuits. Springer Verlag, Berlin / Heidelberg 1919.

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See also