Switching a light accessory on or off is a free action that can only be done once per turn. In other words, you may only switch ONE accessory between ON and OFF once a turn.
* For instance, if you have both a light and a laser on your weapon, you can use a free action to turn the laser ON during Turn 1, but you must wait until Turn 2 to turn the light on or turn the laser off. And so on and so forth.
* If you absolutely must manipulate more than one light accessory on the same turn, you can spend a non-combat action (and therefore, the entire turn) to do so on as many of them as needed on all of your equipped and immediately accessible weapons.
'''NOTE:''' Although some firearms can mount more than one light accessory, the effects of two lights, two lasers, a dual module and a light or a laser, etc. '''do not stack'''. In other words, it's pointless to have more than one light or laser on the same firearm. (Though don't let that stop you if you really want to have 2 laser sights on your rifle...)