As shown in the illustration, by what means are all the 'MS' contacts are opened and closed? EL-0073

Correct Answer: Option A — manual operation of the master switches

Master switches in marine winch control circuits are manually operated devices. The operator physically moves the handle to engage specific contacts, which then complete the control circuit to energize the appropriate contactor coils. This manual input provides the necessary sequence control for hoisting or lowering operations as required by IEEE 45.