Heartsaver First Aid Part I Progress Indicator: Question 2 of 22 2.  The Sentinel electronic monitoring system comprises a sensor unit, switch box, and display unit.  It continuously measures the pressure in the oxygen cylinder and indicates this pressure on the sensor unit, tests and monitors the correct functioning of the BG 4, and generates a warning when the residual pressure is reached, as well as in the event of malfunctions. Choices: True False