Main Page | See live article | Alphabetical index In telecommunication, a four-wire circuit is a two-way circuit using two paths so arranged that the respective signals are transmitted in one direction only by one path and in the other direction by the other path. Note: The four-wire circuit gets its name from the fact that, historically, two conductors were used in each of two directions for full-duplex operation. The name may still be applied, e.g. , to a communications link supported by optical fibers, even though only one fiber is required for transmission in each direction. Contrast with two-wire circuit. Source: from Federal Standard 1037C and from MIL-STD-188 This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.