There are laser sensors built into the artificial grass to check direction, and an acoustic sensor that determines the distance the ball travels.

The first, an acoustic sensor, arms the mine as a helicopter approaches.

Acoustic sensor operators begin their career in the fleet after attending specialized training.

Unlike regular microphones, which measure pressure, the acoustic sensors — which are smaller than a match head — measure air particle velocity.

When used with the passive infra-red fuze, an acoustic sensor detects approaching vehicles and activates the infra-red sensor, which triggers the mine at the optimal moment as the target passes.