Utilizing the existing rail-type connection terminal UK connection technology and installing a circuit composed of electronic components, the transmission coupling of the photoelectric process is realized. The core of automatic control is that the control unit must be reliably isolated from each sensor and actuator to avoid interference. The optically isolated terminals can perform this function well and ensure that the on-site signal matches the low voltage required by the electronic control device. It can also be used as an interface between process control peripherals and controls, signal and regulator devices, and for different voltage and power ranges. Optically isolated terminals have the advantages of signal loss at the control end, high switching frequency, no mechanical contact jitter, no wear switching, high insulation voltage, no fear of vibration, no positional influence and long life, and are therefore widely used in the field of automatic control.

Subject Content and Scope of Application This standard specifies various methods of identifying the terminals of electrical equipment (hereinafter referred to as equipment), and formulates the general rules for identifying equipment terminals and specific wire ends using an alphanumeric system. This standard applies to identification marks of the terminals of equipment (such as resistors, fuses, relays, contactors, transformers, rotary motors, etc.) and combinations of these devices, and also applies to the identification of specific wire ends. When necessary, detailed application of these general rules for certain products and necessary auxiliary identification methods can be given in the relevant standards.