I would recommend a secondary tone warning the user that either the intended target or, in the case of "Proximity Fused" Missiles, a unintended target is too close to the weapon operator. In the case of the Truth Missile Launcher Package which has both "Homing" and "Proximity Fuse", it is too easy to lock on to one high value target and not notice a much closer tango that the missile will have to pass that will cause premature detonation, possibly way to close for the safety of the weapon operator. A different tone might be helpful in that case. Maybe a BIG RED "X" over the target sight. The operator can still shoot the weapon, but will know that the weapon discharge is NOT advised.