The scheme of external connections is a diagram showing the electrical connections between instruments and automation equipment installed on the process equipment, outside the switchboards and on the boards, as well as connecting the wires to the devices and shields. The wiring diagram shows the external connections of the automation cabinet. The diagram shows the cabinet, its input and output elements (connectors, clamps, etc.) and the ends of cables and external cables to them, the data on the connection of the cabinet (external circuit characteristics, addresses, marking) are indicated. The wiring diagram of external postings is executed by a separate document in the presence of single multi-section or composite boards, a large number of junction boxes, group racks of devices, when connections to them make it difficult to read the connection diagram.