SCSI extenders are stand-alone modules or cards used to extend the distance at which peripheral devices may be placed from the host computer. Small computer systems interface (SCSI) is an intelligent I/O parallel peripheral bus with a standard, device-independent protocol that allows many peripheral devices to be connected to the SCSI port. A single SCSI bus can drive up to eight devices or units: the host adapter or controller, and seven other devices. Each device is assigned a different SCSI ID, ranging from 0 to 7.