This type of coma is usually reversible once the blood sugar is corrected. Oxygen deprivation: Oxygen is essential for brain function. Cardiac arrest causes a sudden cutoff of blood flow and oxygen to the brain, called hypoxia or anoxia.
The external power supply is the AC power adapter that converts household AC electricity voltages to the much lower DC voltages needed to charge a mobile phone's internal battery.
With unregulated power adapters, or any other unregulated DC power supply, the DC output voltage is dependent upon an internal voltage reduction transformer, and related to the amount of current used by the electrical load. (The load is the device receiving power from the adapter).