Attenuation-to-crosstalk ratio
Attenuation-to-crosstalk ratio (ACR) is a parameter that is measured when testing a communication link, which represents the overall performance of the cable.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> AcR is a mathematical formula that calculates the ratio of attenuation to near-end crosstalk for each combination of cable pairs.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> ACR is expressed as a figure in decibels (dB), between the signal attenuation produced by a wire or cable transmission medium and the near-end crosstalk (NEXT).<ref name=SearchNetworking>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In order for a signal to be received with an acceptable bit error rate, the attenuation and the crosstalk must both be minimized.<ref name=SearchNetworking/> Crosstalk can be reduced by ensuring that twisted-pair wiring is tightly twisted and is not crushed, and by ensuring that connectors between wire and cable media are properly rated and installed.<ref name=SearchNetworking/>
Positive ACR calculations mean that transmitted signal strength is stronger than that of near-end crosstalk.<ref name=inet>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> ACR can be used to define a signal bandwidth (e.g. 250 MHz for category 6 cable) where signal to noise ratios are sufficient to support certain applications.<ref name=inet/> The maximum frequency for which positive ACR is assured provides a benchmark to assess the usable bandwidth of twisted-pair cabling systems.<ref name=inet/> EIA/TIA specifies specific values for ACR in order to meet the various categories of cable.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>