Can a lightbulb be switched on using two mobile phones? (Make a call and the bulb switches on)
I need this for a kid's school project so the questions like should the bulb keep glowing after the call ends do not bother. Its for a kid's school project so should be as simple as it could be.
I think something like the circuit below is good enough to switch your relay. I only drew the coil of the relay here.