After some more research, the next attempt will be this one http://www.learningaboutelectronics.com/Articles/555-timer-delay-before-turn-off-circuit.php to a relay.

HT:M80,VP150,QS8,EP500 Outside:4xM3 Office:AudioBytes, Rumpus: M60,VP150,M22 Portable:2 x Airs