Diode–transistor logic

Diode–Transistor Logic (DTL) is a class of digital circuits built from bipolar junction transistors (BJT), diodes and resistors; it is the direct ancestor of transistor–transistor logic. It is called diode–transistor logic because the logic gating function (e.g., AND) is performed by a diode network and the amplifying function is performed by a transistor (contrast this with RTL and TTL).