I have a 3-meter-long USB cable, which uses copper #28 AWG wires for these data lines. They are coated with polyethylene insulation, 1 mm thick. The insulation has a relative permittivity of . The data wires are held close to each other, so the insulation of one wire touches the insulation of the other wire. Ignore the impact of the nearby DC and ground wires. Assume all material near the cable has a relative permeability of .

The data rate sent over the cable depends on the version number (1.0, 1.1, 2.0, 3.0, 3.1, 3.2, 4), and in some cases the sub-version (Low Speed, Full Speed, High Speed), as shown in the table below

	USB 1.0 1996	USB 1.1 1998	USB 2.0 2001	USB 2.0 Revised	USB 3.0 2011	USB 3.1 2014	USB 3.2 2017	USB4 2019
Data Rate	1.5 Mbit/s (low speed) 12 Mbit/s (full speed)	1.5 Mbit/s (low speed) 12 Mbit/s (full speed)	1.5 Mbit/s (low speed) 12 Mbit/s (full speed) 480 Mbits/s (high speed)		5 Gbits/s (super speed)	10 bits/s (super speed+)	20 bits/s (super speed+)	40 bits/s (super speed+ and thunderbolt 3)

For which versions and sub-versions should the 3-meter-long cable be treated as a transmission line, and for which versions/sub-versions should ignore the transmission line theory and just treat it using a simple circuit model such as a L1, L2, T or Pi circuit?

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