S> (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)