This series is applicable for 50Hz, with voltage up to 690V and current up to 125A. It is mainly used in electricity circuits with the dimensions 22 x s58 for short-circuit protection (gG/gL, aR and aM) for electric motors and semi-conductor spare parts. This series breaks circuits with impact electric current and expectation short circuit up to 100KA, for insulating. RT18 Ns has two road passes for in and out lines, with function of insulating power supply. RT18 Ls adopts a safe lock for button up device, without mistake operation. This series can also indicate break due to bright light indicator.