GDTs create an effective short circuit when triggered, so that if any electrical energy (spike, signal, or power) is present, the GDT will short this. Once triggered, a GDT will continue conducting (called follow-on current) until all electric current sufficiently diminishes, and the gas discharge quenches. Unlike other shunt protector devices, a GDT once triggered will continue to conduct at a voltage "less than" the high voltage that initially ionized the gas; this behavior is called negative resistance. Additional auxiliary circuitry may be needed in DC (and some AC) applications to suppress follow-on current, to prevent it from destroying the GDT after the initiating spike has dissipated. Some GDTs are designed to deliberately short out to a grounded terminal when overheated, thereby triggering an external fuse or circuit breaker.