The USB 1.1 spec gives well-defined \$V/I\$ characteristics for full-speed output drivers, which can be used to find the series damping resistance, \$R_S\$. The low-speed output schematics also reference \$R_S\$, but it's not entirely clear if it's the same (since low-speed characteristics are typically less strict than full-speed). And while the spec states:
In the rest of the chapter, references to the buffer assume a buffer with the series impedance unless stated otherwise.
Does that mean it applies to both low-speed and full-speed, or just full-speed? If it's the latter case, then what's the valid range of \$R_S\$ for low-speed output drivers?