This is something ive been wondering about for a while. In the RGB cartoon, there was a button on the handle closest to the body that you pushed to fire the thrower.

On the EGB, they pulled a trigger like a gun on their thrower.

What did they use in the movie? Since i built my pack, i added a button onto the box that the two pipes go into following Paranorman's plans. I know they flip a regular switch to power up, but what do they use to fire?

the trigger on the movie props is the push bottin on the trigger box

Note the sticker above the pushbutton as well: “Intensify”

its the toggle switch below the monebtary push button switch.

no it was the push button that fired the beam out of the gun. as i siad in a old post “after watching the movies for a few mins i came up with this, in gb2 the toggle switch under the push switch turns on the pack and gun (master switch), the bottom one one the right apreartly is like kinda like a safty switch, (when in the down postion it does not turn off the gun jsut keeps it from fireing) so it does not accdently fire when hanging on the belt since the fire switch is a push switch on the gun. wich would also expline the x if you ever been in some fighterplans they have x's on some switchs, the top one on the right i belive to be a kill switch for the pack,
”

http://www.ghostbusters.net/disscussion/ghm/1/23542/

In my set up im using one switch to turn on lights on pack, 1 switch to turn on the lights on the gun, and the other one to turn on the bargraph display on the gun, then of course thiers the push button switch, which should be the kind that you have to hold down… not the kind that you press and it stays on…