(electric)

If the operator doesn't open the gun for a set time, a relay shuts off power to the control circuit.  This eliminates the opportunity for system damage from operator neglect. This option can save hundreds of dollars in downtime per year.  You don't have "all the beef",  until you have this option as insurance. Machines that are particularly quiet or in a different area from the operators are  often  left  running  for long periods of  time.