Final answer:
The AN/DSM-129 missile test set operates on battery power in direct current mode. In submarines, the power from batteries can create a magnetic field that may affect unshielded compasses.
Step-by-step explanation:
In the direct current battery mode, the AN/DSM-129 missile test set operates using power from the battery itself. The AN/DSM-129 is a piece of diagnostic equipment used to ensure the functionality of various missile systems. In the context of nonnuclear submarines, when submerged, they utilize batteries for power. The electrical current supplied by these batteries can create a magnetic field.
Specifically, a magnetic field can be calculated at a distance from a wire carrying electric current, such as the 1200 A directed to the submarine's drive mechanism. If the wires leading to and from the drive mechanism are placed next to each other, the cumulative magnetic field might change due to the counteracting effects of the currents in opposite directions. Such magnetic fields could potentially disrupt the readings of an unshielded compass on the submarine.