Jean Morbern’s work created a singularity that vibrated at a fixed probability frequency. By using this as a referent, it was possible to transfer that person along the timestream; in other words, to travel in time.
To transfer through time, people or objects enter a transference chamber, a perfectly spherical steel chamber whose interior, once the doors are shut, is entirely cut off from outside quanta. A probability field of a precise frequency is generated inside the chamber, and its contents are displaced through time. A recall time and place is prearranged with the travellers; at a certain time, and in a certain place, a field exactly inverse to their transmission field will be generated from the College into the past. If they are standing at the correct point, they will be recalled to the College.
Only objects of the right probability frequency will be recalled, and if two time travellers from different periods were standing side by side, only the one matching the recall field would disappear. However, it is possible to bring back items from the past by the use of probability tags, which change an object’s frequency to match the recall field.
It is possible to set the coordinates for a transference manually, but it is generally left up to the Register to handle the process.
The Register is also in charge of making sure no paradoxes occur and that Morbern’s Code is observed. No one is sent back to a time where they could meet themselves; no one can travel into their personal future beyond the Home Time; if you spend five hours in the past (“upstream”) then the Register will bring you back five hours after you left. This is so taken for granted that sometimes even experienced College personnel fall into the trap of thinking that such things are actually impossible, not just prevented … which suits the Register perfectly.