This is the circuit of a constant voltage battery charger, probably for floating a 12V sealed lead acid battery.
Many years ago the company I worked for constructed and sold many of these with almost identical circuit.
Diode D1 prevents reverse biasing of the LM317 if incoming power is switched off or fails, while the battery is
still connected. Without D1, under this condition the LM317 is likely to release its smoke.
Diode D2 protects against reverse connection of the battery. If reverse connection does occur, (hopefully) a
downstream fuse will blow and the charger stays intact. Personally I would use a more beefy diode in this
location (say a 5A device) so that under short circuit conditions, it can blow a 2A fuse without damage to itself.
and, by the way, what are the best healthful lifestyle hacks?
Following are the healthy lifestyle hacks you should consider:-
When you’re at restaurant. Wash your hands after giving order because the menu is the dirtiest thing you can touch.
When feeling depressed, do some cleaning.
Drinking chocolate milk has been proven to help relieve muscle soreness after the workout.
Gargle salt water after taking meal, if you are unable to brush.
Eat an orange before workout. It’ll keep you hydrated and will not let your muscles getting sore.