A great way to spend an afternoon in a hot stuffy classroom staring at screen, whilst you are being screamed at over the headset by a Company OC who is sitting only 5 feet behind you, wondering why you find it impossible to get rounds on target on time in the specified manner in a nice warm classroom. In the meantime whilst trying not to fall asleep on your nyrex, and leaving non permanent ink marks all over your face, you are wondering why the odd red shaped blobs on the screen turn black when hit and the battlefield is not permanently scarred with the awesome firepower you have just dumped on some poor Russian's head who happens to be sitting happily in a field somewhere near Bovey Tracey minding his own business. That said treated like a computer game its awesome fun!
The Invertron, a hot stuffy room in which a screen, projector, speakers and many small monitors and radios are to be found all to aid in the training of Arty TAC parties. Every type of battlefield fire support is available from the 81mm Mortar to Naval Gunfire and the legendary Grid Square Removal System. A quaint piece of the UK or sometimes somewhere further afield is displayed whilst you attempt to bomb the hell out of it. No permanent damage is done to the display unless you are lucky enough to hit a bright red target which may turn black. All ammunition types in service are available and suitably poor graphical interpretations of their effects are displayed on screen. Particularly comical is airburst HE!
A favourite of the UKLF OP competition of old, OP parties would be forced to crawl into a 'hole' constructed solely from classroom desks and be forced to conduct their Fire Mission by staring out a small letter box whilst a SMIG would jump up and down on the desk, letting off the odd Smoke Grenade and playing old WW2 soundtracks whilst white blobs representing the Third Shock Army would slowly approach you on the screen.
Invertron was replaced by Invertron AFCT, and both replaced the puff range. The original Invertron was done with slides and multiple projectors. AFCT was a computer generated jobbie that worked on a telejector.