refer respiratory care text books man
It is used for the breaths in rescue breathing & CPR.
Ambu bag is used for giving breaths; advantage is you get more oxygen into victim than breathing into them with your breaths.
Artificial maneuver breathing unit
It is used to administer the breaths. It is more effective than mouth to mouth as it will provide air at 21% oxygen vs, 16% oxygen from air via the lungs.
Artificial manual re-breathing unit