The 7405 IC package contains six independent positive logic NOT GATES (INVERTERS). Pins 14 and 7 provide power for all four logic gates. The Open-Collector outputs require pull-up resistors for proper logical operation.
[NOT SIMULATION]  [NOT-TRUTH-TABLE]
	Since the outputs of the 7405's gates are open-collector, they can be directly tied together to logically form different logic blocks without the need of seperate gates. The picture to the left illustrates the coupling of 3 NOT gates. The LED will light if any of the 3 inputs (A,B,or C) are LOW and only go out if all input (A,b,and C) are HIGH. In this way the circuit is behaving like a 3 input NAND gate. NOT GATE Logic-Rules: The output is the inverse of the input, in otherwords if the input is HIGH then the out put is LOW and if the input is LOW the output is HIGH.