How does a proximity fuse typically function in a PGM?

A proximity fuse operates by sensing the distance to a target and detonating when it is within a predetermined range, which maximizes its effectiveness. This method allows the fuse to explode the warhead at an optimal moment, increasing the likelihood of damage to the target without requiring a direct hit. This is particularly useful for precision-guided munitions (PGMs), as it enhances their lethality against harder targets or those in motion, ensuring that the explosive force effectively impacts the target area.

The other options focus on different mechanisms that do not accurately reflect how a proximity fuse works. Detonation upon impact would require a direct strike, which can be less effective for certain targets, while time-based triggers do not consider the target's position. Activating at maximum altitude is not a standard function of proximity fuses, which instead rely on distance measurement to optimize detonation timing.