We're now going to make a pulse delayed circuit using a NAND gate. This circuit does not produce an output immediately when it is turned ON, but only after the lapse of a pre-determined time.
For comparison with this circuit, we'll make another circuit that generates an output immediately when it is switched ON.
Take a look at the schematic for this project. You'll see that the circuit made up of IC1 and Q1 generates an output immediately when S1 is pressed, so LED 2 also lights up immediately when S1 is pressed.
This doesn't happen with the other circuit made up of IC2 and Q2; it gives out an output after the lapse of a delay time determined by C (combined capacitance of C1 and C2 with 50µF) and R2. Turn power ON and press S1 to see the delayed operation.