* Whenever voltage is supplied to pin 2 (trigger input), it's usually less than 1/3 of supply voltage.
* The lower comparator output forces the flip flop to a low logic state which means output stage has a reversing action.
* It can be stated that when the output of the flip flop is low, the output of the 555 timer goes high.
* Whenever power is connected to an astable circuit, the timing capacitor off pin 6 is discharged.
* The voltage at pin 2 becomes 0V and the output of timer is driven high.
* The capacitor off pin 6 starts charging through the resistors off pins 6, 7 and 8.
* The capacitor off pin 6 is also the input threshold of the timer.
* The internal flip flop toggles as the voltage across the capacitor off pin 6 increases above 2/3 value of the power supply voltage.
* Subsequently, pin 7 becomes low which makes the capacitor off pin 6 to begin the process of discharging.
* As soon as the voltage across capacitor off pin 6 goes below 1/3 of the supply voltage the internal flip flop resets and pin 7 becomes high.
* Once again when the capacitor off pin 6 starts charging the process continues the cycle.
* This is only possible if the IC (in this example a 555 timer) is in good working condition.
* The flashing of the LEDs is dependant upon the charging and discharging frequencies.
* Pin 5 provides stability and access to the internal voltage divider (2/3 Vcc) and it should be noted that it's omission wouldn't make any observable operational difference to the circuit.
