Quantum discriminator

From Memory Alpha, the free Star Trek reference.

The quantum discriminator was a piece of 31st century technology found in a temporal communicator that was used to focus in on a certain frame of time, making targeting a specific date and time a lot simpler than without one.

Crewman Daniels stated to Jonathan Archer that in his high school, there was a quantum discriminator on every desk. (ENT: "Shockwave, Part II")