What type of reserve does a J valve provide?

The J valve is designed to provide a built-in reserve of air for divers. This feature means that the reserve air is integrated into the valve's design, automatically giving the diver access to an additional supply of air once the main supply is depleted. This type of reserve is crucial in emergency situations, as it allows divers to have a safety net during their ascent or while experiencing unexpected complications underwater. The built-in nature of this reserve eliminates the need for separate systems or additional equipment, enhancing the diver’s safety by ensuring that the air reserve is readily available when needed.