This slide shows the transmission line model of a short cable element with its linear and reactive components. The graph follows the cable length versus data rate characteristic. At low data rates the maximum cable length is determined by the DC resistance of the cable. When the cable resistance approaches the value of the termination resistor, the voltage divider action between the resistances diminishes the signal by -6dB. For a 24AWG, 120 Ω, UTP cable this occurs at around 1200m or 4,000ft. The roll-off section presents the transition from low to high data rates. Here the reactive components of the transmission line kick in making the losses of the transmission line frequency dependent. Thus, with increasing data rate the cable length must be reduced. At high data rates the cable lengths become very short and are typically determined by a jitter budget. The diagram shows that for a data rate of 20 Mbps and 5% jitter, the maximum cable length is about 250ft (75m). However, when allowing for up to 20% jitter, the cable length can almost be doubled to around 450ft (137m).