TTL stands for :

The correct answer is option 1):Transistor-Transistor Logic

Concept:

• Transistor–Transistor Logic (TTL) is a class of digital circuits built from transistors and resistors. It is called transistor–transistor logic because the logic function (e.g., AND) and amplification is performed by transistors.
•  A TTL input signal is defined as "low" when between 0 V and 0.8 V with respect to the ground terminal.
• A TTL input signal is defined as "high" when between 2 V and 5 V. if a voltage signal ranging between 0.8 V and 2.0 V is sent into the input of a TTL gate, there is no certain response from the gate and therefore it is considered "uncertain" (precise logic levels vary slightly between sub-types and by temperature).
• Two input TTL NAND Gate was given as

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