anchor.diff:  Passive gate is similar to the regular pump except:
   * It doesn't require power
   * Can not transfer low pressure to higher pressure (so it's more like a valve where you can control the flow)
  +* Passes gas when output pressure lower than target pressure
   
   */
   
  
positive.code: 	icon_state = "passgate_map-3"
  
  	name = "passive gate"
  	desc = "A one-way air valve that does not require power."
  
  	can_unwrench = TRUE
  	shift_underlay_only = FALSE
  
negative.code: 				pressure = text2num(pressure)
  				. = TRUE
  			if(.)
  				target_pressure = clamp(pressure, 0, ONE_ATMOSPHERE*100)
  				investigate_log("was set to [target_pressure] kPa by [key_name(usr)]", INVESTIGATE_ATMOS)
  	update_icon()
  
  