differential line

hardware A kind of electrical connection using two wires,

one of which carries the normal signal (V) and the other

carries an inverted version the signal (-V). A differential

amplifier at the receiver subtracts the inverted signal from

the normal signal to yield a signal proportional to V. This

subtraction is intended to cancel out any noise induced in the

wires, on the assmption that the same level of noise will have

been induced in both wires. Twisted pair wiring is often

used to try to ensure that this is the case.

The two wires might be connected at the receiver to separate

analogue to digital converters and the subtraction performed

digitally.

The RS-422 serial line standard specifies differential

drivers and receivers, whereas the earlier RS-232 standard

does not.

Opposite: single ended.

(1995-03-08)