Based on the decals and button/dial types this operating manual is probably what the prop builders had in mind when they designed this prop. It makes sense when you consider the 5 red circular decals next to the bar graph on the wand, and the aluminum round dial marked 1, 2, 3.
The wand has 3 metal toggle switches on the gun body and a button (Labelled intensify) which fires.
Power= lower metal switch close to the bottom of the bargraph (near SLO-BLO label)
Generator= metal switch above it.
Activate=labelled on picture
1. Power off, Generator off, Activate off= Pack turned off. Bar graph off
2. Power on, Generator off, Activate off= Turns on proton pack main power but does not fire up cyclotron
3. Power on, Generator on, Activate off= Runs system checks and turns on indicator lights. Bar graph powers on and sits at empty circle decal, no stream
4. Power on, Generator on, Activate on= Powers on cyclotron. Ready to fire. Bar graph at quarter circle, quarter power stream (lowest possible positron output)
(In point 4. above, the Bar graph scales all the way up and down -once- when Activate is hit because it is finding and settling into the Positron output level pre-selected (if any) and it settles and comes to rest at that level.)
5.a. Power on, Generator on, Activate on, Positron output dial to +1= Bar graph at half circle, half stream
5.b. Power on, Generator on, Activate on, Positron output dial to +2= Bar graph at three quarter circle, three quarter stream
5.c. Power on, Generator on, Activate on, Positron output dial to +3= Bar graph at full circle, full stream (highest positron output)
I can't believe how easy it was to figure out!
In the image above the positron output dial (metal circle with 1, 2 , 3 markings) is set to default. (Neither +1, +2 or +3). In fact when Egon says, "Venkman shorten your stream, I don't want my face burned off." you can see Murray reaching for the positron output dial with his left hand. (PS: This is exactly how the Matty Collector Neutrona wands operate.)
The extending barrel mechanism (green lever next to "Intensify" button) makes most sense if you think of it as an extra safety mechanism. You need multiple safety levels with something this destructive.
When you try to fire it with a non extended barrel the red light flashes quickly indicating it's not ready. (just like the Matty Collector Neutrona wands).
Safety for storage:
The rotating handle. Something you can't do by accident. Rotate the handle and the grip isn’t ergonomic to hold with both hands anymore. It indicates the device is disarmed and the switches can not turn it on. It prevents the switches being accidentally snagged or turned on by accident while in transport.
So much thought has gone into the design of this. Kudos to the Matty guys for figuring part of it out so well.