4001 is a very versatile CMOS chip.
It contains 4 NOR gates.
Minimum supply voltage 3v
Maximum supply voltage 15v
Max current per output 10mA
Maximum speed of operation 4MHz
Current consumption approx 1uA
Follow the inputs and note when the LED is illuminated.
The secret to understanding the operation of
the gate is show in the diagram on the right.
It is called GATING.
When one input is held LOW, the signal on the other input
will be inverted by the gate and appear on the output.
When one input is held HIGH, the output is a constant LOW.
This is also shown
in the 1kHz tone circuit below.
Do not leave an input "open" (non-connected) as the high input
impedance (approx 10M) will pick up noise and create faulty
Circuits built around a CD 4001: