resistor transistor logic (IC) (RTL)
The circuits of logics differ in the logic elements and in the supply voltages, logic levels and switching times.
Resistor Transistor Logic (RTL) is one of the oldest logic families, it was developed already in the sixties. RTL uses resistors and transistors or diodes as logic elements, then as DTL logic. RTL logics consist of bipolar transistors and resistors. The emitters of all transistors are at reference potential, the collectors are connected together and have a common working resistor. The supply voltage was 3.6 V.