Attenuation-to-crosstalk ratio, ACR, is the most important result when testing a link because it represents the overall performance of the cable.[1] ACR is a mathematical formula that calculates the ratio of attenuation to near-end crosstalk for each combination of cable pairs.[2] 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).[3] In order for a signal to be received with an acceptable bit error rate, the attenuation and the crosstalk must both be minimized.[3] 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.[3]
Positive ACR calculations mean that transmitted signal strength is stronger than that of near-end crosstalk.[4] ACR can be used to define a signal bandwidth (i.e. 200 MHz for category 6) where signal to noise ratios are sufficient to support certain applications.[4] The maximum frequency for which positive ACR is assured provides a benchmark to assess the usable bandwidth of twisted-pair cabling systems.[4] EIA/TIA specifies specific values for ACR in order to meet the various categories of cable.[5]