This is a refit (minor changes) to the previous model of this I posted last year. (Which never got a video or anything else). All the specs of the major components are outlined above. The simple question is what does all that stuff together do? Well the simple answer answer is that it moves the 6 NXT balls around in a circle continuously through a series of 'gags'.
The 'gags' (in order): Gate (below conveyor belt): Holds the ball till' the lifter arm is fully down. Lifter: Lifts the ball up where it is pushed out onto the conveyor belt. Ejector: Pushes ball off lifter onto the conveyor belt. Conveyor belt: Carries a ball to the pivot arm. Pivot Arm: Senses a ball on the belt from the ultrasonic sensor. Tilts to drop ball onto escalator. Escalator: Carries a ball upward and drops it onto the hold. Hold: Holds two balls and releases one with a pneumatic cylinder. Center Rack: Carries a ball from the hold to the grabber arm. Grabber Arm: Senses a ball using a color sensor. Carries a ball over to the swing lifter. Swing Lifter: Lifts a ball up to the platform ejector with a swing motion. Platform Ejector: Carries ball to the pneumatic hold and pushes a ball on to it. Pneumatic Hold: Holds a ball until there isn't a ball at the gate. And then the cycle repeats.
The RCXs communicate with each other using infrared while the NXTs communicate with each other over bluetooth. A NXt light sensor monitors light from one LED attached to an RCX. When that light is on the NXTs know that they can run. However, if the light is out, they will not start or they will abort their current program (if there's a problem).
Stop switch: That little box with the wheel is a plunger that pushes on a touch sensor which tells the RCXs to stop. Since the NXTs monitor if the RCXs are active, they will also stop when that is pushed down.