ELG series automatic security grating is small in shape, high in precision, and has strong ability of signal transmission and reception. The control principle is that the light emitting signal is directly accepted by the light receiver, forming a protective light curtain, the light receiver monitors the on-off state of the light curtain, and the on-off signal of the light curtain is processed through the internal circuit, and directly output low level (light through) or high level (light blocking), through the transmission line to the PLC or alarm circuit. Implement device stop or send security alarm.