(2B1Q) A physical layer encoding used for Integrated Services Digital NetworkBasic rate interface. 2B1Q represents two Bits (2B - a "diBit") using one of four signal levels (1Q - a "quadratude"). The first Bit of the diBit is indicated By polarity: positive indicates a Binary 1 and negative indicates a 0. The second half of the diBit is indicated By voltage magnitude: 1 Volt indicates a Binary 1 and 3 Volts indicates Binary 0. (2003-01-10)