For safety cables, insulation of the electrical conductor is the main consideration, since it must continue to function perfectly in a fire for the duration of rescue and firefighting work. The insulation must not burn or cause short circuiting. Before, such cables had to be custom made. Now, novel special silicone rubber grades are simply applied to the copper conductor. In a fire, the silicone rubber burns. However, instead of ash, a very hard ceramic layer is produced, which provides adequate electrical insulation event at temperatures of around 1,000 °C. Such insulated conductors are ideal for manufacturing modern safety cables.