When activated these systems generate a temporary transportation porthole, which has the appearance of a large orange ball of energy. This porthole transports anyone who passes through it to the "nearest" habitable environment. The system is completely random and crew members will often be sent to different planets (though they will all arrive at the same temporal coordinates). As there is no way to return to a TARDIS via the portholes, the device is only used when a TARDIS's destruction is imminent.