A temporal chamber was a room aboard a Suliban helix that allowed audio and minimal visual communications between Cabal soldiers and a mysterious figure from the 28th century. The room produced a strange "pre-echo" effect, in which it appeared that one could see things happen seconds before they actually did. This resulted in the room and everything in it being distorted and some events happening in somewhat slowed or fast motion. It was also dangerous to fire at least certain directed energy weapons in the room, an example being phase-pistols. If such a weapon was fired, the initial energy beam was made harmless before a subsequent and more intense pulse would surge through the beam and result in a shockwave throughout the room. (ENT: "Broken Bow", "Cold Front")
When Silik was temporarily unable to contact his master, Captain Jonathan Archer used the chamber to make his way back to his time from the 31st century, using an advanced technology provided by Crewman Daniels that was able to temporarily transform the chamber into a means by which one could physically travel through time. According to Daniels, the technology was something his people learned in high school and modifying a communicator and hand scanner to have a similar effect wasn't terribly difficult with the right tools such as an amount of copper. After returning to his own time, Archer destroyed the chamber and the device from Daniels' quarters used to allow him to return to his own time. (ENT: "Shockwave, Part II")
Background information Edit
This room is unnamed on screen; the name "temporal chamber" comes from the scripts for all the episodes it is depicted in.
The temporal chamber was described at length in the revised final draft script of "Broken Bow", which referred to it as "Dimly-lit, filled with labyrinthine technology. The room is bisected by an archway that creates a rippling barrier of energy. This is a place where people from two different time frames can briefly coexist; the Suliban come here to meet with visitors from a distant century." It was further detailed that the room, "on opposite sides of the barrier," also contained "identical high-tech podiums" for the communicating persons to stand at. The teleplay then went on to describe the "pre-echo" effect, calling it "strange" and explaining, "We can see and hear things a split-second before they happen. It's a disquieting and eerie feeling of two worlds slightly out of phase with each other." 
For "Broken Bow", the temporal chamber was built as a set on Paramount Stage 16. (Information from "Broken Bow" call sheets)
The final draft script of "Shockwave, Part II" stated, "The pre-echo effect runs throughout all scenes in this room." However, this is not true of how the room is depicted in that episode.