According to "The Original Series" ("TOS") writers' guide, the effective range of a transporter is 40,000 kilometers, although thick layers of rock can reduce this range ("TNG": ""). The "TOS" episode "" however, appears to indicate that the transporters' maximum range, during that time period in "Star Trek" history, is actually around 30,000 kilometers. Transporter operations have been disrupted or prevented by dense metals ("TNG": ""), solar flares ("TNG": ""), and other forms of radiation, including electromagnetic ("TNG": ""; "TNG": "") and nucleonic ("TNG": ""), and affected by ion storms ("TOS": ""). Transporting, in progress, has also been stopped by telekinetic powers ("TNG": "") and by brute strength ("TNG": ""). The "TNG" episode "" features a dangerous and experimental "subspace transporter" capable of interstellar distances and the Dominion had the ability to transport over great distances ("DS9": ""). The 40,000-kilometer limit is also referred to in "ENT": "".