This failsafe is a unconventional one, which is a time limit failsafe, and without a gas saver unit.
This one will prevent you diving when your gas tank was empty, you can forget the dive & surface cycles when a voyage with a full charge. when your gas tank is low gas, the failsafe will locks the gas servo to blow, and preventing diving again.
If you use the failsafe, you'd better record your sub driver's gas tank total blow time with a stopwatch(no blow cycles) at first, and setting a safe blow time limit for count down. The save time=total gas blow time - one blow time of sub from underwater to surface - one blow time of sub from underwater to surface.
This one is suit every types Sub-Driver, you can setting the best blow time by yourself (MIX 20 secs.)
1.ordinary failsafe,when signal loss, It will control gas servo to blow, unless restart the failsafe switch.
2 safe blow time, if your setting a safe blow time for your Sub-Driver, it will control gas servo to blow when your gas tank low gas, unless restart the failsafe switch.