High Voltage Differential: the logic signalling system originally defined in the SCSI-2 standard. HVD has a maximum logic voltage of 5V and uses a paired plus and minus signal level to reduce the effects of noise on the SCSI bus. It was functionally replaced by LVD (Low Voltage Differential) in the SCSI-3 variant of the standard. HVD and LVD SCSI are not directly compatible but can be interconnected by the use of a special adapter.
High Voltage Differential. A method of driving SCSI cables, which is being replaced by LVD.
High Voltage Differential. A type of SCSI differential signaling requiring more expensive hardware to handle the higher voltage. HVD became obsolete with the introduction of SCSI-3.
A derivation of Ultra SCSI that allows for the use of data cable lengths up to 25 meters.
High Voltage Differential. A logic system used in some SCSI drives. It uses a paired plus and minus signal to reduce the effects of noise on the SCSI bus. Any noise injected into the signal would be present in both a plus and minus state, thereby being canceled.
High Voltage Differential. Uses two wires, transmitting a signal on one and its inverse on the other. At the receiving end, the difference between the two signals is measured and interpreted. Noise on the bus will affect both the signal and its inverse equally, so the difference between the two lines will remain the same and the noise can not be misread as a signal.