This being DC Universe, the Treadmill was developed for Barry Allen to travel through time to fight aliens who had taken over the Earth in 2287. Kid Flash traveled to the past to stop the aliens from projecting their hive into the future while the Flash battled the aliens in the Future.
The Treadmill is oprerated by menas of running on it REALLY fast in order to reach/bridge the inter-dimensional gap. To select the destrination time one must set the treadmill marker to the appropriate period. The treadmill works by generating vibrations that will shift the user into a specific time. The vibrations require a high amount of speed to generate, and attempts to use the treadmill without it have proved dangerous. Initially, the vibrations had to be kept up internally, or one would fade back into the time from whence they came.
The cosmic treadmill allows anyone with superpeed to precisely travel time. It also allowed travel between the multiple Earths. Since the treadmill needs a speedster in order to function, in many stories a working one can be found inside the Flash Museum. Since few people have the speed to have it work, it is usually seen as an exhibit, though at times it has been stored in the archives. It is shown that over time the Treadmill can become unstable and unreliable, and cause extreme stress to the mind of the user.
According to this source, The Cosmic Treadmill was calibrated in Roemers, where one Roemer is the speed of light, much as Mach 1 is the speed of sound. The unit was named after the Danish astronomer Ole Rømer, who first measured the speed of light, as Mach numbers are named after Ernst Mach. To the best of my knowledge, the Roemer unit was invented for the comic book. - See more at:
Things to remember while using The Cosmic Tredmill:
- Useless if you have no superspeed
- Keep up your internal vibrations
- Do not use it too often as it may cause severe stress
adopted from: wikipedia.org