direct coupled transistor logic (IC) (DCTL)
DCTL logics, Direct Coupled Transistor Logic (DCTL), consist of directly coupled bipolar transistors. In these first logic circuits, there were only resistors in addition to the directly coupled transistors.
In DCTL logics, the bases are directly connected to the inputs without an intermediate base resistor. Without this resistor, DCTL logics are simpler in design and easier to manufacture than RTL logics, which have a base resistor.