Performance index of twisted pair(2)

3. DC resistance
The DC loop resistance consumes part of the signal and converts it into heat. It refers to the sum of the resistance of a pair of wires. The DC resistance of the 11801 twisted pair must not be greater than 19.2 ohms. The difference between each pair should not be too large (less than 0.1 ohm), otherwise it indicates poor contact, and the connection point must be checked.
4. Characteristic impedance
Different from the loop DC resistance, the characteristic impedance includes the resistance and the inductance impedance and the capacitance impedance with a frequency of 1 to 100MHz. It is related to the distance between a pair of wires and the electrical properties of the insulator. Various cables have different characteristic impedances, and twisted-pair cables have 100 ohms, 120 ohms and 150 ohms.
5. Attenuation crosstalk ratio (ACR)
In some frequency ranges, the proportional relationship between crosstalk and attenuation is another important parameter that reflects cable performance. ACR is sometimes also expressed in terms of signal-to-noise ratio (SNR: Signal-Noice ratio), which is calculated from the difference between the worst attenuation and the NEXT value. A larger value of ACR indicates stronger anti-interference ability. General system requirements are at least greater than 10 decibels.
6. Cable characteristics
The quality of the communication channel is described by its cable characteristics. SNR is a measure of the strength of the data signal taking into account the interference signal. If the SNR is too low, it will cause the receiver to be unable to distinguish between the data signal and the noise signal when the data signal is received, which will eventually cause data errors. Therefore, in order to limit the data error within a certain range, a minimum acceptable SNR must be defined