If it really is "the big red button", it might be worth renaming this switch on the wiki page into something better. Literal translation of the switch is "drive" and can, as you had pointed, indicate several systems and not just hydraulics. The confusing thing is that I can turn on/off laser without turning drive switch first. And to fire a laser you do not need any hydraulics, gyros, etc. The LED display should indicate laser reading which is then sent to FCS to adjust the reticle (if set on AUTO). We used completely different system on M84 so I hope some one will shed some light on TPD-K1