2B1Q
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Two-binary, one-quaternary (2B1Q) is a physical layer encoding used for Integrated Services Digital Network (ISDN) basic rate interface. 2B1Q uses four signal levels, which are -450 mV, -150 mV, 150 mV and 450 mV, each (1Q) equivalent to two bits (2B). A competing encoding technique, also used for ISDN basic rate interfaces, is 4B3T.
2B1Q is also used for some variants of HDSL.
This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.
