Cable adaptors are available that allow the connection of external Small Computer System Interface devices to the common Universal Serial Bus port. This enables use of many scanners, printers and other devices with computers lacking SCSI ports.
The two main options when purchasing such a cable adaptor are the Ratoc U2SCX and the Adaptec USBXChange. Both have 50-pin connectors and operate under Windows or Mac OS.
SCSI to USB cable adaptors simply plug into external USB ports and connect to SCSI computer accessories. The adaptor may require installation of a driver (see its instructions). Such adaptors usually have a cable from one end to the other, not a direct one-piece converter.
These adaptors were not designed for use with internal hardware devices. Drivers for some older SCSI equipment may not remain available for modern operating systems. Also, attaching USB-based accessories to a SCSI port generally remains impossible.