diode transistor logic (Chip) (DTL)
DTL logics consist of diodes, transistors and resistors. From this circuit technology, the standard logics AND gate, OR gate and NOT gate are manufactured in thick-film and thin-film technology, as well as in monolithic construction. In DTL logics, diodes form the OR or AND gate, which is inverted via a NOT gate formed by a transistor.
In the NAND gate, the two diodes with the resistor form the AND gate. If there are HI levels ("1") at both inputs, the two diodes block and the base of the transistor receives the base current via the resistor. The transistor goes into saturation and the logic level goes to emitter potential, i.e. LO level. If only one input has a LO level ("0"), the corresponding diode opens and pulls the base potential towards zero; the transistor blocks, the output level goes to "1".
DTL technology was discontinued due to high power consumption and unsatisfactory switching times. DTL technology has evolved from DRL logic(Diode Resistor Logic).