Unbalanced Line
- Pair of conductors to carry signals which have unequal impedances along their lengths and to ground and other circuits
- Examples: Coaxial cable, Earth Return Telegraph
Balanced Line
- Pair of conductors to carry signals which have equal impedances along their lengths and to ground and other circuits
- It reduces common-mode noise and interference when fed to a differential device such as a transformer or differential amplifier
- It eliminates common-mode noise because it has equal impedances, even if the signalling scheme is single-ended
  - That is, just like differential signals, the voltage differential eliminates the common-mode noise, with the original signal retrieved.
  - However, the difference is that due to the polarity being the same, the retrieved signal will have a voltage which is the difference of the wires, while differential signals will have double the voltage due to opposing polarities.
- Examples: Twin-lead cable, Twisted Pair cable (reduces EM interference from crosstalk too)

Notes

Twisted Pair cable may be shielded for additional noise immunity - Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP) cables
- Twisted Pair Cables are used to eliminate common mode noise in both differential signalling and in single ended signalling.
- Different rates of twist are used for lines in the same cable to avoid crosstalk.
Coaxial cables were described by the Telegrapher's equations, used in Transatlantic submarine telecommunication cables.
Balanced lines are not to be confused with differential signalling, which is a signalling scheme.

Backlinks

Left-click: follow link, Right-click: select node, Scroll: zoom