GB/T 18656-2025 Industrial Systems, Installations and Equipment and Industrial Products - Identification of Terminals within a System
1 Scope
This document establishes general principles for the identification of terminals of objects within a system, applicable to all technical areas (for example mechanical engineering, electrical engineering, construction engineering, process engineering). They can be used for systems based on different technologies or for systems combining several technologies.
Requirements for marking of terminal designations on products are not part of this publication.
Note: The document is based on the general principles for the structuring of systems including structuring of the information about systems, established in the International Standard ISO/IEC 81346 series, published jointly by IEC and ISO.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 6988.1-2024 Preparation of documents used in electrotechnology - Part 1: Rules (IEC 61082-1:2014, IDT)
Note: The referenced content of GB/T 6988.1-2024 has no technical differences from the referenced content of IEC 61082-1:2006.
IEC 60417 Graphical symbols for use on equipment
Note: GB/T 5465 (all parts), Graphical symbols for use on electrical equipment (IEC 60417 Database)
IEC 60445 Basic and safety principles for man-machine interface, marking and identification – Identification of equipment terminals and conductor terminations
Note: GB/T 4026-2025, Basic and safety principles for man-machine interface, marking and identification - Identification of equipment terminals, conductor terminations and conductors (IEC 60445:2021, IDT)
IEC 60757 Code for designation of colours
Note: GB/T 13534-2009, Code for designation of colours (IEC 60757:1983, IDT)
IEC 81714-3 Design of graphical symbols for use in the technical documentation of products - Part 3: Classification of connect nodes, networks and their encoding
Note: GB/T 16901.3-2009, Rules for the presentation of graphical symbols - Graphical symbols for use in the technical documentation of products - Part 3: Classification of connect notes, networks and their encoding (IEC 81714-3:2004, IDT)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
object
entity treated in a process of development, implementation, usage and disposal
Note 1: The object may refer to a physical or non-physical “thing”, i.e. anything that might exist, exists or did exist.
Note 2: The object has information associated to it..
[GB/T 5094.1-2018, 3.1, modified]
3.2
system
set of interrelated objects considered in a defined context as a whole and separated from their environment
Note 1: A system is generally defined with the view of achieving a given objective, e.g. by performing a definite function.
Note 2: Elements of a system may be natural or man-made material objects, as well as modes of thinking and the results thereof (e.g. forms of organisation, mathematical methods, programming languages).
Note 3: The system is considered to be separated from the environment and from the other external systems by an imaginary surface, which cuts the links between them and the system.
Note 4: The term “system” should be qualified when it is not clear from the context to what it refers, e.g. control system, colorimetric system, system of units, transmission system.
Note 5: When a system is part of another system, it may be considered as an object as defined in this document.
[GB/T 2900.83-2008, 151-11-27, modified]
3.3
aspect
specified way of viewing an object
[GB/T 5094.1-2018, 3.3]
3.4
function
intended or accomplished purpose or task
[GB/T 5094.1-2018, 3.5]
3.5
product
intended or accomplished result of labour, or of a natural or artificial process
[GB/T 5094.1-2018, 3.6]
3.6
component
product used as a constituent in an assembled product, system or plant
[GB/T 5094.1-2018, 3.7]
3.7
identifier
attribute associated with an object or system to unambiguously distinguish it from other objects or systems within a specified domain
[GB/T 5094.1-2018, 3.10, modified]
3.8
reference designation
identifier of a specific object formed with respect to the system of which the object is a constituent, based on one or more aspects of that system
[GB/T 5094.1-2018, 3.11, modified]
3.9
terminal
point of access to an object intended for connection to an external network
Note 1: The connection may refer to: a) a physical interface between conductors and/or contacts, or piping and/or duct systems to provide a signal, energy or material flow path; b) an association of functional nature established between logical elements, software modules, etc. for conveying information.
Note 2: The external networks may be of different nature and accordingly they may be classified. IEC 81714-3 provides such classifications.
3.10
terminal designation
identifier of a terminal with respect to the object to which it belongs, related to one defined aspect
3.11
terminal designation set
group of terminal designations, each identifying the same terminal from different aspects
3.12
object designation
identifier of a specific object in a given context
Note: Examples of such designations are: reference designation, type number, serial number, name.
[GB/T 26853.1-2011, 3.13, modified]
4 Terminal designation
4.1 General
Terminals establish the interface of objects for connecting them to other objects in a network, for example connecting to an electrical network, logic function network, logic network in software, piping network, etc.
An object may be associated with any number of terminals.
Each terminal shall be unambiguously identified with respect to the object itself as well as to the system to which this object belongs.
Figure 1 illustrates the principle of constructing an unambiguous terminal designation.
Contents
Foreword I
1 Scope
2 Normative references
3 Terms and definitions
4 Terminal designation
4.1 General
4.2 Designation of terminals with respect to the product aspect
4.3 Designation of terminals with respect to the function aspect
4.4 Designation of terminals with respect to the location aspect
4.5 Terminal designation set
5 Classification of terminals
Annex A (informative) Examples of terminal designations not specified by a manufacturer
Bibliography
Figure 1 Principle of terminal designation
Figure 2 Example of designation of terminals for a 3-phase squirrel-cage motor
Figure 3 shows an example of a device with function labels and terminal markings of the terminals shown.
Figure 4 Example of a symbol for a motor starter provided with terminal designations related to the function aspect
Figure 5 Example of a terminal board for cross-connection where the terminals are designated related to their location aspect
Figure 6 Example of a terminal designation set
Figure 7 Example of a design with terminal designations related to the function aspect
Figure 8 Example of an implemented design based on Figure 7 with terminal designations related to the product aspect
Figure 9 Example of an implemented design based on Figure 7 with terminal designation sets related to the function and product aspects
Figure A.1 Four terminal blocks composing one terminal assembly (each terminal block is considered as an object)
Figure A.2 One terminal block with eight terminals (the complete unit is an object)
Figure A.3 One terminal block with eight terminals with two entry points each
