What do the initials TTL stand for?

The initials TTL stand for Transistor-Transistor Logic. This technology refers to a class of digital circuits built from bipolar junction transistors (BJTs) and resistors. The distinguishing aspect of TTL is that both the logic functions and the amplification are performed by transistors, which allows for faster switching times and increased noise immunity compared to earlier logic families.

Transistor-Transistor Logic is foundational in digital electronics and has been widely used in the design of various integrated circuits, notably in the creation of early computers and a range of other digital devices. The name reflects the emphasis on using transistors for both the logic gates and signal amplification, which has made TTL circuits very efficient in many applications.

The other options refer to different concepts or types of logic circuits that either do not exist in conventional terminology or do not accurately relate to the widely recognized TTL classification.