(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)