CREATE TABLE table_204_583 (id DECIMAL, "capacitor type" TEXT, "capacity" TEXT, "volts" TEXT, "temp." TEXT, "energy-to-weight ratio" TEXT, "power-to-weight ratio" TEXT)

which capacitor has the top voltage rating ?
SELECT "capacitor type" FROM table_204_583 ORDER BY "volts" DESC LIMIT 1
SELECT "capacitor type" FROM "table_204_583" ORDER BY "volts" DESC NULLS LAST LIMIT 1