Temporal conduit

From Memory Alpha, the free Star Trek reference.

The temporal conduit is a device that allows travel through time. A group of Na'kuhl led by Vosk, having escaped to 1944 Earth, attempted to return to their own 29th century by constructing a temporal conduit in New York City. However, they were forced to use local materials, that they secured through an alliance with Nazi Germans. The primitive technology used made the machine enormous, and the Na'kuhl had difficulty keeping the conduit stable for more than a few seconds. After several failed attempts to operate the temporal conduit, the Na'kuhl were eventually successful, although the NX class starship Enterprise destroyed the device moments before the Na'kuhl could enter it. (ENT: "Storm Front, Part II")