400px, right Attenuation-to-crosstalk ratio (ACR) is a parameter that is measured when testing a

communication link A data link is the means of connecting one location to another for the purpose of transmitting and receiving digital information (data communication). It can also refer to a set of electronics assemblies, consisting of a transmitter and a recei ...

, which represents the overall performance of the cable. AcR is a mathematical formula that calculates the ratio of

attenuation In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variabl ...

near-end crosstalk In electronics, crosstalk is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, i ...

for each combination of cable pairs. ACR is expressed as a figure in decibels (dB), between the

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...

attenuation produced by a wire or cable transmission medium and the near-end crosstalk (NEXT). In order for a signal to be received with an acceptable

bit error rate In digital transmission, the number of bit errors is the number of received bits of a data stream over a communication channel that have been altered due to noise, interference, distortion or bit synchronization errors. The bit error rate (BER) ...

, the attenuation and the crosstalk must both be minimized. Crosstalk can be reduced by ensuring that

twisted-pair Twisted pair cabling is a type of wiring used for communications in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted ba ...

wiring is tightly twisted and is not crushed, and by ensuring that connectors between wire and cable media are properly rated and installed. Positive ACR calculations mean that transmitted signal strength is stronger than that of near-end crosstalk. ACR can be used to define a

signal bandwidth Bandwidth is the difference between the upper and lower frequencies in a continuous band of frequencies. It is typically measured in hertz, and depending on context, may specifically refer to ''passband bandwidth'' or ''baseband bandwidth''. ...

(e.g. 250 MHz for

category 6 cable Category 6 cable (Cat 6) is a standardized twisted pair cable for Ethernet and other network physical layers that is backward compatible with the Category 5/5e and Category 3 cable standards. Cat 6 must meet more stringent ...

) where signal to noise ratios are sufficient to support certain applications. The maximum frequency for which positive ACR is assured provides a benchmark to assess the usable bandwidth of twisted-pair cabling systems.

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specifies specific values for ACR in order to meet the various categories of cable.

References

Telecommunication theory {{Telecomm-stub