The trick is to employ GOOD projectionists and engineers who know what they are doing and can maintain the equipment so that such events never happen in the first place. What good is a call on the radio "hey moron, the film is wrapping" from a machine? The show is still ruined (as well as the print) and I'm not even sure if your contraption could notify the projectionist faster than a customer anyway.
Paul
Now, if you were talking INFRARED... you have my attention. Yes, there is still the chance for unwanted operation but the difference is you can control the access points to the system. You have to be within X feet of an emitter/receiver for the remote to work. By putting them in areas with restricted access you can further reduce chances of interference.
Put an infrared port on the back of each projector, and maybe one or two on the ceiling of the main booth hallway, etc. Then network them all together and maybe have a computer as the "hub" of the system and you might have a pretty righteous setup on your hands!
So what's the remote control device? Easy! A Palm computer! Just point your Palm computer at the port on any projector and tap the screen. You can check up on the status (or remotely start, if you dare) each projector in the system. The Palm can even be programmed with the showtime schedule so that it can beep to remind you when to start the shows.
Even though it would be too expensive for any regular theatre to install a system like that, let alone get anybody to maintain it, it has been a little ongoing gedanken experiment with me. (Excess windshield time gives you lots of opportunity to think about silly stuff like that.
)
The wireless (RF) stuff is quite susceptible to interference, specifically the police department that is right next door that is on an adjacent frequency! We have an integrated remote control system from AMX/Panja ( http://www.panja.com ) that is user programmable with an infinite number of peripherals. Our system integrates audio switching and volume, video switching, cinema processor input switching, a box o' relays for projectors, surveillance cameras, and slide projectors into a snazzy interface that can be operated by my laptop, a touch-screen, two-way RF touch-screens, etc. The possibilities are endless, however the practicality of it all sometimes stops me short of making some rediculous change.
For example, it would only take about a day and a thousand dollars to upgrade the system to the point that from anywhere in the world I could:
Unlock the theatre doors
Turn on the lights
Turn on pre-show music and slides
Dim the lights and start the show
Adjust framing and focus (monitored via closed circuit TV)
Adjust the volume
And lock up at the end of the night
And then I would be out of a job, since I wouldn't have to show up anymore! The systems are fun to build and play with, but I would be totally screwed the second I got a few hundred miles away only to discover a brain wrap.