These temperature resistant single-conductor cables are used for the internal wiring of lighting fixtures, heaters, electrical machinery, switching systems and distributors in equipment and plant and machinery, suitable for installation on, in and beneath plaster, in closed installation ducts, as well as for traffic systems and outdoor applications. These cables are not approved for direct routing on racks, gutters or tanks. For a protected installation, these cables may be used at a nominal voltage of up to 1000 V alternating current or a direct current up to 750 V when grounded. The maximum operating d.c. voltage used in rail vehicles shall not exceed 900 V when grounded. Hook-up wire (hookup wire) is a single conductive wire.