Resistor-transistor logic

Resistor-transistor logic (often referred to by its acronym, RTL) was the earliest logic circuit family using bipolar transistors; it was later essentially completely replaced by the later diode-transistor logic.

The name comes from the fact that the logic functions were performed by resistor networks; the signal-amplification was performed by a transistor. The use of resistors was good in the pre-IC stage (when discrete transistors were expensive), but it limited the number of inputs.

Is it notable as being the logic family in the first integrated circuits, produced by Fairchild Semiconductor; those ICs were used in the Apollo Guidance Computer.

External links

• RTL article on Wikipedia - has comprehensive coverage of the topic