In telecommunication

Telecommunication

Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...

, a longitudinal voltage is a voltage

Voltage

Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...

 induced or appearing along the length of a transmission medium

Transmission medium

A transmission medium is a material substance that can propagate energy waves...

.

Note 1: Longitudinal voltage may be effectively eliminated by using differential amplifiers or receivers that respond only to voltage differences, e.g., those between the wires that constitute a pair.

Note 2: Induced longitudinal voltages at low (power-line

Electric power transmission

Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...

) frequencies can be greatly reduced by twisting parallel wires to create what are referred to as "twisted wire pairs." Synonym common-mode voltage.