Editing Ground loop (electricity) (section)

==In digital and RF systems==
In digital systems, which commonly transmit data serially ([[RS-232]], [[RS-485]], [[USB]], [[FireWire]], [[DVI]], [[HDMI]] etc.) the signal voltage is often much larger than induced power frequency AC on the connecting cable screens. Of those protocols listed, only RS-232 is single-ended with ground return, but it is a large signal, typically + and - 12V, all the others being differential. 

Differential signaling must use a balanced line to ensure that the signal does not radiate and that induced noise from a ground loop is a common-mode signal and can be removed at the differential receiver.

Many data communications systems such as Ethernet [[10BASE-T]], [[100BASE-TX]] and [[1000BASE-T]], use [[DC-balanced]] encoding such as [[Manchester code]]. The ground loop(s) which would occur in most installations are avoided by using signal-isolating transformers.

Other systems break the ground loop at data frequencies by fitting small [[ferrite core]]s around the connecting cables near each end or just inside the equipment boundary. These form a [[common-mode choke]] which inhibits unbalanced current flow, without affecting the differential signal.

[[Coaxial cable]]s used at radio frequencies may be wound several times through a [[ferrite core]] to add a useful amount of common-mode inductance. This limits the flow of unwanted high-frequency common-mode current along the cable shield.

Where no power need be transmitted, only digital data, the use of [[fiber optics]] can remove many ground loop problems, and sometimes safety problems too. Optical isolators or [[optocouplers]] are frequently used to provide ground loop isolation, and often safety isolation and can help prevent fault propagation.