Question 288Electricity & Electronics - Assistant Engineer

The correct answer is D) manual operation of the master switches. The illustration EL-0073 depicts the wiring diagram for the 'MS' contacts, which are used to open and close the circuits. In this case, the 'MS' contacts are operated manually, meaning the master switches are physically operated by hand to open and close the contacts. This is the typical method for controlling critical electrical systems on marine vessels, as it provides the operator with direct control over the circuits. The other answer choices are incorrect because they do not accurately describe the means of operation shown in the illustration. Operating coils, magnets, and solenoid switches are not the means by which the 'MS' contacts are opened and closed in this specific diagram.