A Veritable Almanac!
The circuit opposite shows the modification needed in order to make the astable function as a simple flashing light utilising a light emitting diode.
The cicuit is shown below of a dummy car alarm which flashes the LED when the ignition is turned off.
The Astable Multivibrator is a basic two stage amplifier with 100% of its output fed back in phase with its input. This results in a free running oscillator whose output signal is only limited by the power supply voltage rails.
The cicuit can be used as a clock pulse generator for logic circuits.
In this instance it is going to be used to form the basis of a "Dummy" car alarm.