7401 QUAD 2-Input NAND GATE POSITIVE LOGIC
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.
with open-collector outputs
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.