Refers to the manner in which SCSI signals are placed on the cable. Single ended drives one signal line against ground while differential SCSI drives two signal lines. The signal is the voltage difference between the two lines. Differential drive has greater noise immunity than single-ended, especially when used with twisted pair cable which converts noise to common mode voltage that is more easily rejected. This greater noise immunity allows substantially longer SCSI cabling of up to 25 meters (82 feet) for HVD and 12 meters (39.4 feet) for LVD versus 6 meters (19.7 feet) or less for single-ended. Differential and single-ended SCSI are not compatible on the same bus segment without an electronic device such as a SCSI converter to convert between differential and single-ended. With rare exception, no software (driver) modifications are necessary for conversion between single-ended and differential. HVD has no requirement for other than passive terminators. Single ended terminators should be active and multimode LVD terminators must be active. HVD SCSI was rendered obsolete in the SPI-3 document of SCSI-3.

This definition is in context to SCSI. See more contextual defintions for Differential SCSI.