Target box

We're not sure why it has the letter 'N' on the side of it in Cybertronix.

Target boxes are small flying devices intended for use as target practice. They can simulate energy signatures.

Fiction

Beast Wars cartoon

When unveiling the first autogun to his Predacon troops, Megatron programmed a target box with a Maximal energy signature and sent it to fly around. The autogun promptly locked on and destroyed it. Megatron pronounced the results "excellent" and told his men he intended to build a lot more autoguns and turn the area into a death trap for Maximals. Power Surge