SCSI terminators are electrical circuits placed at each end of a SCSI cable for impedance matching. They are an important part of any small computer system interface (SCSI) that uses hard drives, CD-ROMs, scanners, tape drives, or other SCSI peripherals controlled by a SCSI bus. SCSI terminators are used to close off both ends of the system that begins with the bus. Many different types of SCSI terminators are available. The most common types are passive, active, active negation, high-voltage differential (HVD), low-voltage differential (LVD), multimode (LVD / MSE), forced perfect terminator (FPT), and high- byte terminator (HB).