Cerebro amplifies the brainwaves of the user. In the case of telepaths, it enables the user to detect traces of others worldwide, also able to distinguish between humans and mutants. Depictions of its inherent strength have been inconsistent; at times in the storylines it could detect mutated aliens outside of the planet, when at others it could only scan for mutants' signatures in the United States. It is not clear whether it finds mutants by the power signature they send out when they use their powers or by the presence of the X-gene in their body; both methods have been used throughout the comics. Using Cerebro can be extremely dangerous, and telepaths without well-trained, disciplined minds put themselves at great risk when attempting to use it. This is due to the psychic feedback that users experience when operating Cerebro. As the device greatly enhances natural psychic ability, users who are unprepared for the sheer enormity of this increased psychic input can be quickly and easily overwhelmed, resulting in insanity, coma, permanent brain damage or even death. The one exception has been Magneto, who has been said to have minor or latent telepathic abilities as well as experience amplifying his mental powers with mechanical devices of his own design. Some mutants have learned to shield themselves from Cerebro, usually via their own telepathic ability. Magneto can shield himself from the device through use of minimal telepathic powers; in the film series, he does so with a specially constructed helmet. Originally, Cerebro was a device similar to a computer that was built into a desk in Xavier's office. This early version of Cerebro operated on punched cards, and did not require a user (telepathic or otherwise) to interface with it. A prototype version of Cerebro named Cyberno was used by Xavier to track down Cyclops in the "Origins of the X-Men" back-up story in X-Men Volume 1 #40. In the first published appearance of Cerebro, X-Men Volume 1 #7, Professor X left the X-Men on a secret mission (to find Lucifer) and left Cerebro to the new team leader, Cyclops, who used it to keep track of known evil mutants and to find new evil mutants. The device also warned the X-Men of the impending threat posed by the non-mutant Juggernaut prior to that character's first appearance. Later, the device was upgraded to the larger and more familiar telepathy-based technology with its interface helmet. More recently, following the example set by the X-Men films, Cerebro has been replaced by Cerebra (referred to as Cerebro's big sister), a machine the size of a small room in the basement of Xavier's School For Higher Learning. Though designed to resemble the movie version of Cerebro, Cerebra is much smaller than the films' version. It resembles a pod filled with a sparkling fog that condenses into representations of mental images.