Line driver output is the signal transmission line using the exclusive IC between the transmission side and reception side. The line driver removed the noise from the original signal by subtracting invert signal from non-invert signal (differential output). This is the transmission method which is conformable to EIA RS-422A standard.

For totem-pole output, open collector output and collector output, the original signal is the potential difference between a signal and COM. If COM gets a noise voltage, the potential difference from the signal becomes smaller and makes the high- low judgment very hard. It causes the error of transmission. For line driver, the original signal is the subtraction between invert signal and non-invert signal (differential output), so that the potential difference does not become smaller and it is effective for the noise.