In order to facilitate on-site construction and maintenance, the components are centrally placed and made into a plug-in type, which greatly saves the time of construction and maintenance. The outer cover adopts blue transparent flame-retardant outer cover.

The resistance-capacitance capacitor is used to absorb and consume the self-induced electromotive force generated by the inductive load when the circuit is disconnected, and can prevent the switch contacts from burning out. It can effectively suppress the instantaneous oscillation and high-frequency current of the operating overvoltage, and slow the waveform of the overvoltage. The steepness and amplitude reduction, coupled with the damping effect of the resistance, make the high-frequency oscillations decay rapidly.