In the DC traction system, due to the existence of operating current and short circuit current, may cause the return circuit (running rail) and the earth to produce a safety beyond the safety of the contact voltage. In this case, it is necessary to assemble a set of rail potential limiting devices between the return circuit (running rail) and the earth, also known as short-circuiting devices, to limit the potential of the operating rails and to avoid the occurrence of contact voltages beyond safety approvals.

Features
　　1 using conventional high-performance DC contactor (or thyristor and DC contactor in parallel with the multiplex switch) to meet the safety requirements of the European standard EN;
　　2 using thyristor short circuit, low maintenance;
　　3 rapid response, to maximize the guarantee Personnel and facilities safety;
　　4 compact design, easy installation;
　　5 live without more debugging, the factory has been put into operation conditions.