How this automatic power on off circuit works?

Herewith attached the automatic power on circuit of an car audio. It is used as auto power on when there is audio input. Audio amplifier starts working after some time of audio signal input.
When there is no signal for 30 seconds it becomes automatically off.

This circuit is not becoming off after 30 seconds. many times it is on for long hours in car even when audio signal is not present. Kindly explain me how to modify or remove this problem. So please guide about working of this circuit.

The picture will not show in my browser.

I only see this part of your image, to give an answer we need to see all of it.