(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)