diode resistor logic (DRL)

DiodeResistor Logic (DRL) consists of diodes and resistors and corresponds to the input circuits of DTL logic.

AND and OR gates as DRL logic

In an AND gate in DRL logic, the diodes are biased across the working resistor and block. The logic level then corresponds to the supply voltage. If a diode has a LO level at the cathode, the current flows across the diode and the output state is "0".

The situation is different with the OR gate. If an input is at HI potential, the corresponding diode conducts and the output also becomes "1".