Target discriminator

Target discriminators were components of starship's weapons systems designed to isolate a target from nearby objects, thereby preventing unwanted impacts.

In 2152, Malcolm Reed, chief tactical officer of Enterprise NX-01, issued an order to keep the ship's target discriminators aligned, as he didn't want one of their torpedoes "mistaking one of [Enterprise's] nacelles for an enemy vessel." (ENT: "Singularity")