Main Page | See live article | Alphabetical index Two-binary, one-quaternary (2B1Q) is a physical layer encoding used for Integrated Services Digital Network basic rate interface. 2B1Q uses four signal levels (1Q), equivalent to two bits (2B). This article (or an earlier version of it) contains material from FOLDOC, used with permission. Update as needed. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.