The Princeps exerts command over his war engine by the means of a Mind Impulse Unit -- a technologically complex neural input device which allows for a cybernetic connection between the human mind and a Titan's Machine Spirit, and the ability to impose his or her will upon it. To establish the link between the Machine Spirit and the human mind requires that the Princeps submit to extensive cybernetic augmentation of his or her central nervous system, either by accepting the implantation of a several cybernetic implants at the back of the neck and skull, a series of implants in the spine which enable the linking of the MIU to the spinal cord or even undergoing entombment in an amniotic tank with large parts of the body rewired to accomodate cybernetic interaction with the Titan.