Differential signaling
Differential signaling is a method for electrically transmitting information using two complementary signals. The technique sends the same electrical signal as a differential pair of signals, each in its own conductor. The pair of conductors can be wires (typically twisted together) or traces on a circuit board. The receiving circuit responds to the electrical difference between the two signals, rather than the difference between a single wire and ground. The opposite technique is called single-ended signaling.
Differential pairs are usually found on printed circuit boards, in twisted-pair and ribbon cables, and in connectors.
Advantages
Provided that the source- and receiver impedances in the differential signalling circuit are equal, external electromagnetic interference tends to affect both conductors identically. Since the receiving circuit only detects the difference between the wires, the technique resists electromagnetic noise compared to one conductor with an un-paired reference (ground). The technique works for both analog signaling, as in balanced audio—and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express, DisplayPort, HDMI, and USB.