I have installed a small set of computer speakers inside my letterbox. I've kept the volume very soft so it doesn't annoy the neighbours - but if I see people standing out the front I'll turn up the volume (from inside the house). This has me thinking - any one know of a circuit/kit can could be wired to a PIR to adjust volume accordingly? Or even just switching the speakers on/off... PIR >> Relay on + countdown timer started >> Relay off > > speaker's 12VDC power ??? Any one got a similar idea?