7401 QUAD 2-Input NAND GATE POSITIVE LOGIC
with open-collector outputs
The 7401 IC package contains four independent positive logic NAND GATES with open-collector outputs. Pins 14 and 7 provide power for all four logic gates. The outputs require pull-up resistors to function properly. The open-collector outputs can be connected together to produce higher output voltages or to implement an active-LOW wired-OR function or active-high wired-AND function with out the need for additional logic gates.
In the figure to the left the LED will only light if all inputs are LOW, in this way the circuit is acting like a 4 input NAND gate.
NAND GATE Logic-Rules:
If both inputs are HIGH then the output will be LOW, otherwise output will be HIGH. See 7400 for more information.