Here's a simplified explanation of how the NE555 adjustable frequency pulse generator works:

Resistor and Capacitor Configuration: You connect external resistors and capacitors to specific pins on the NE555 to set the timing parameters. The values of these components determine the frequency and duty cycle of the output waveform.

Timing Components Charge and Discharge: The NE555 charges and discharges a capacitor based on the values of the connected resistors and capacitors. This charging and discharging cycle generates a voltage waveform across the capacitor.

Output Generation: The voltage waveform across the capacitor is used to trigger the NE555's internal comparator, which toggles the output between high and low states. This action produces a square wave output with a frequency and duty cycle determined by the timing components.

Adjustment: By changing the values of the resistors and capacitors, you can adjust the frequency and duty cycle of the generated pulse waveform. This allows you to create pulse signals with various characteristics for different applications.