I use two 12v outputs on my PJ...one to control the electric screen and the other switches on the extraction fan for my hush box. You could also use it to turn on other bits of kit such as your sub or power amp I think. Cheers, Lee
It can also be used to trigger a speaker to select monopole or dipole if you have speakers that suupport it. In essence 'trigger' means it will initiate any device that has a 12v trigger ability, PJ, Electric Screen, electric curtains etc etc