 The voltage presented to the following stage is pulled low if any one or more of the base–emitter junctions is forward biased, allowing logical operations to be performed using a single transistor.Multiple-emitter transistors replace the diodes of diode–transistor logic (DTL) to make transistor–transistor logic (TTL), and thereby allow reduction of switching time and power dissipation.Logic gate use of multiple-emitter transistors was patented in 1961 in the UK and in the US in 1962.