The circuit described here can be used to develop a fake  alarm. In this system, LED’s glows slowly, becomes brighter and then dims again. This circuit is based on LM358 IC which is an operational amplifier.LM358 consist of two independent high gain operational amplifier in one package. Important feature of this IC is that we don’t need independent power supply for working of each comparator for wide range of power supply. LM358 can be used as transducer amplifier, DC gain block etc.LM358 has large dc voltage gain of 100dB. This IC can be operated on wide range of power supply from 3V to 32V for single power supply or from ±1.5V to ±16V for dual power supply. And it also supports large output voltage swing.The circuit described here uses an opamp to produce a triangular wave, which makes LED’s glow slowly, get brighter and then slowly become off. Similar cycle is repeated.