The redoubts are entered via either the gateways, or by huge blast doors. One unusual aspect of the main doors is that they are all keyed to be opened and closed by using the same combination. 352 to open, 253 to close.
One of the functions of the gateway is that it has an automatic reset button. If this button is pressed within 30 minutes of arrival, it will trigger the correct code to return the user to the gateway they came from.
It seems that the Redoubts are all part of some sort of project known as the Cerberus project. It is revealed that not only are the Matter Transmitters part of this project, but that the white coats seem to have delved into time travel experiments using the same technology.
In Dectra Chain it is learned that project Cerberus is only a small part of a huge project. It was part of Overproject Whisper, which in turn is part of the Totality Concept. It is also discovered that there may be a space station hidden on the other side of the moon, which is completely self sufficient and may have survived the war intact.
In Bloodlines, it is discovered that there is another cog in the Totalitarian Concept wheel. This one is known as Enterprise Eternity, which, for all intent and purposes, appears to have something to do with immortality. Another is project Genesis, which delved into the realm of genetic engineering.
One aspect of the Totality Concept was automation. Even if the enemy managed to get in a sneak attack, the United states would still be able to launch its own missiles, ensuring that the other side was devastated.
Another function revealed by Doc tanner is the fact that unless a destination code is entered the jump is always random.
In Ice and Fire it discover that during the evacuations of the redoubts, one of the first things that would have been destroyed would have been the manuals and the software backups for controlling the gateways. They also learn from Rick Ginsberg that there are two more Cryonic facilities that he knows of. One is located near Duluth, the other is located in Texas, near the Grande. Rick also told them a code to enter into the gateway controls which will prevent them from jumping into a gateway that is damaged or malfunctioning.
Several side effects are common when ever a jump occurs. The most common effect are nightmares. Nausea, nose and ear bleeds, weakness, and dizziness are also known to occur.
In Dark Carnival they discover the codes for several gateways as well as the LD button which allows them to return to the last destination if they use it before initiating a jump.
In Moon Fate it is hinted that a malfunctioning gateway may lengthen the time it takes to jump from one gateway to another. A prime example is that it was only late November when Jak left the group, but the next time they meet up, over eight months have passed and Christina Balenger is pregnant, well into her third trimester.