The maximum currents are the same as in USB spec. 2.0:
low-power: 100mA
high-power: 500mA
Read about that in chapter 7.2.1 "Classes of Devices" and chapter 7.3.2 "Electrical Characteristics" of USB spec. 1.1
Any idea abt the basic building block of USB Transmitter compliant to 1.1?
As any general purpose IO Transmitter has Pre-Driver and Driver Circuits...I mean to say USB Transmitter has any other blocks other than Pre-Driver and Driver?