Linjepar

Linjepar, or line pair, is a term used to describe a set of two electrical conductors that form a single circuit between two points. In telecommunications and electrical networks, a linjepar typically consists of two insulated wires that carry a signal or power and present a defined impedance to the connected equipment. Linjepar are a common arrangement in copper-based transmission, such as local telephone loops, where the two conductors connect a subscriber’s equipment to a central office or distribution frame.

A key feature of linjepar is that the two conductors operate together as one signal path, with the return path provided by the companion conductor. To reduce electromagnetic interference and crosstalk between adjacent pairs, the wires are often twisted together, a configuration known as a twisted pair; shielding may be added in harsher environments. The concept of a linjepar is thus closely tied to the broader idea of multi-pair cables, where many such two-wire pairs run in parallel within a single sheath.

Performance characteristics depend on conductor material, gauge, insulation, shielding, and the impedance the line presents to the transmitter and receiver. Historically, traditional telephone line pairs had a nominal impedance around 600 ohms, while modern twisted-pair networks, such as those used for data, typically use differential impedances around 100 ohms.

Common issues affecting linjepar include open circuits, short circuits, insulation faults, and crosstalk from neighboring pairs. Faults are typically detected through continuity tests, insulation resistance measurements, and, in more complex installations, time-domain reflectometry.

In practice, linjepar remain a basic building block of wired communication, serving simple two-wire connections even as higher-capacity multi-pair and fiber systems expand network design.