USR5638 is a part of US Robotics' V.92/56K Faxmodem Pro. It is a high-speed external modem designed for use with desktop and laptop computers. The modem has a high data transmission rate up to 56K bps downstream and up to 48K bps upstream. It also supports V.44 compression and Internet call waiting. It is compatible with both USB and serial ports and is certified for use with Windows and Mac operating systems.