Question

The fundamental switching action of a ttl gate is based on a

Answer 1

Transistor–Transistor Logic (TTL) is a class of digital circuits built from bipolar junction transistors (BJT), and resistors. It is called transistor–transistor logic because both the logic gating function (e.g., AND) and the amplifying function are performed by transistors (contrast this with RTL and DTL). It is notable for being a widespread integrated circuit (IC) family used in many applications such as computers, industrial controls, test equipment and instrumentation, consumer electronics, synthesizers, etc. Because of the wide use of this logic family, signal inputs and outputs of electronic equipment may be called "TTL" inputs or outputs, signifying compatibility with the voltage levels used. 
History 

TTL became popular with electronic systems designers in 1962 after Texas Instruments introduced the 7400 series of ICs